Heating system for fiber-reinforced thermoplastic feedstock and workpiece

ABSTRACT

An additive manufacturing system is disclosed that comprises two or more lasers for precisely heating a fiber-reinforced thermoplastic feedstock and a fiber-reinforced thermoplastic workpiece in preparation for depositing and tamping the feedstock onto the workpiece. The system employs feedforward, a variety of sensors, and feedback to ensure that the feedstock and workpiece are properly heated.

CROSS-REFERENCE TO RELATED APPLICATIONS

The following are hereby incorporated by reference:

-   (i) U.S. Pat. No. 10,076,870, entitled “Filament Guide,” issued on    Sep. 18, 2018; and-   (ii) U.S. patent application Ser. No. 15/959,213, entitled    “Variable-Contour Compaction Press,” filed on Apr. 21, 2018; and-   (iii) U.S. patent application Ser. No. 15/959,214, entitled    “Variable-Contour Compaction Roller,” filed on Apr. 21, 2018; and-   (iv) U.S. patent application Ser. No. 15/959,215, entitled    “Self-Cleaning Variable-Contour Compaction Press,” filed on Apr. 21,    2018; and-   (v) U.S. patent application Ser. No. 16/023,197, entitled “Filament    Cutter,” filed on Jun. 29, 2018; and-   (vi) U.S. patent application Ser. No. 16/023,210, entitled “Filament    Accumulator or Tensioning Assembly,” filed Jun. 29, 2018; and-   (vii) U.S. patent application Ser. No. 16/690,765, entitled “Heater    for Thermoplastic Filament and Workpiece,” filed Nov. 21, 2019; and-   (viii) U.S. patent application Ser. No. 16/792,150, entitled    “Thermoplastic Mold with Tunable Adhesion,” filed on Feb. 14, 2020;    and-   (ix) U.S. patent application Ser. No. 16/792,156, entitled    “Thermoplastic Mold with Implicit Registration,” filed on Feb. 14,    2020; and-   (x) U.S. Patent Application Ser. No. 63/025,109, entitled “Heating    System for Fiber-Reinforced Thermoplastic Feedstock and Workpiece,”    filed May 14, 2020, and-   (xi) U.S. Patent Application Ser. No. 63/029,172, entitled “Heating    System for Fiber-Reinforced Thermoplastic Feedstock and Workpiece,”    filed May 22, 2020.

For the purposes of this specification, if there is any inconsistency inthe language between this specification and the language in one or moreof these documents, the language in this specification prevails.

FIELD OF THE INVENTION

The present invention relates to additive manufacturing in general, and,more particularly, to an additive manufacturing process that usessegments of fiber-reinforced thermoplastic feedstock (e.g., pre-pregtape, filament, etc.) as its elemental unit of fabrication.

BACKGROUND OF THE INVENTION

In the same way that a building can be constructed by successivelydepositing bricks on top of one another, it is well known in the fieldof additive manufacturing that an article of manufacture can befabricated by successively depositing segments of fiber-reinforcedthermoplastic filament on top of one another.

In some ways, a segment of thermoplastic filament is similar to aspaghetti noodle. When the temperature of a thermoplastic filament isbelow its resin softening point, the filament is long, thin, stiff, andnot sticky—like a dry spaghetti noodle. In contrast, when thetemperature of the filament is above its resin softening point but belowits melting point, the filament is long, thin, flexible, and sticky—likea wet spaghetti noodle.

There are, however, some key differences between bricks andthermoplastic filament. For example, masonry bricks are not, in and ofthemselves, self-adhesive, and, therefore an adhesive compound—typicallymortar—is used to bind them together. In contrast, segments ofthermoplastic filaments are self-adhesive, and they will become bound ifthey are pressed tightly when they are hot and held together until theyare cool.

Similarly, it is well known in the field of additive manufacturing thatan article of manufacture can be fabricated by successively depositingsegments of thermoplastic tape on top of one another. Whereas a segmentof thermoplastic filament is similar to spaghetti, a segment ofthermoplastic tape is similar to a ribbon pasta or lasagna noodle. Whenthe temperature of the thermoplastic tape is below its resin softeningpoint, the tape is long, thin, wide, stiff, and not tacky—like a drylasagna noodle. In contrast, when the temperature of the tape is aboveits resin softening point but below its melting point, the tape is long,thin, wide, flexible, and sticky—like a wet lasagna noodle. And likethermoplastic filament, segments of thermoplastic tape areself-adhesive, and they will become bound if they are pressed tightlywhen they are hot and held together until they are cool.

FIG. 1 depicts an illustration of additive manufacturing system 100 inthe prior art, which system fabricates articles of manufacture bysuccessively depositing segments of fiber-reinforced thermoplasticfeedstock (e.g., filament, tape, etc.) on top of one another.

Additive manufacturing system 100 comprises: platform 101, robot mount102, robot 103, build plate support 104, build plate 105, workpiece 106,deposition head 107, tamping tool 108, controller 109, feedstock reel110, feedstock 111, accumulator 112, laser 141, optical cable 151,optical instrument 161, laser beam 171, laser control cable 191,irradiated region 271, nip line segment 281, pinch line segment 282, anddeposition path 291, interrelated as shown.

FIG. 2a depicts a close-up of workpiece 106, deposition head 107,tamping tool 108, feedstock 111, optical cable 151, optical instrument161, and laser beam 171, as depicted in FIG. 1. FIG. 2b depicts aclose-up of workpiece 106, deposition head 107, tamping tool 108,feedstock 111, irradiated region 271, and deposition path 291, alongcross-section AA-AA, as depicted in FIG. 2a . FIG. 3 depicts a schematicdiagram of the heating architecture for additive manufacturing system100.

Platform 101 is a rigid metal structure that ensures that the relativespatial relationship of robot mount 102, robot 103, deposition head 107(including tamping tool 108), and optical instrument 161 are maintainedand known with respect to build-plate support 104, build plate 105, andworkpiece 106. Robot mount 102 is a rigid, massive, and stable supportfor robot 103 that provides ballast and inertial stability for robot103. Robot 103 is a six-axis articulated mechanical arm that holdsdeposition head 107, optical instrument 161 and optical cable 151. Themovement of robot 103 (including deposition head 107) is under thedirection of controller 109. Robot 103 is capable of depositingfeedstock 111 at any location, in any one-, two-, or three-dimensionalcurve, and with any angular orientation.

Build plate support 104 is a rigid, massive, and stable support forbuild plate 105 and workpiece 106. Build plate support 104 comprises astepper motor—under the direction of controller 109—that is capable ofrotating build plate 105 (and, consequently workpiece 106) around anaxis that is normal to the X-Y plane. Build plate 105 is a rigidaluminum-alloy support onto which workpiece 106 is steadfastly affixedso that workpiece 106 cannot move in any direction or rotate around anyaxis independently of build plate 105. Workpiece 106 comprises one ormore segments of feedstock 111 that have been successively deposited andwelded together in a desired geometry. Deposition head 107 is the endeffector of robot 103 and comprises:

-   -   (i) a feedstock guide that directs feedstock 111 into position        for heating, tamping, and welding onto workpiece 106, and    -   (ii) tamping tool 108, which tamps the heated feedstock 111 into        the heated workpiece 106, and    -   (iii) a feedstock cutter—under the direction of controller        109—that periodically or sporadically cuts feedstock 111, and    -   (iv) optical instrument 161, which takes laser beam 171 from        optical cable 151, conditions it, and directs it onto irradiated        region 271, and    -   (v) a structural support for optical instrument 161 that        maintains the relative spatial position of the feedstock guide,        tamping tool 108, the cutter, and optical instrument 161.        The feedstock guide, the feedstock cutter, and the structural        support for optical instrument 161 are omitted from the figures        so that the reader can more clearly understand the functional        and spatial relationship of workpiece 106, deposition head 107,        tamping tool 108, feedstock 111, and optical instrument 161.

Tamping tool 108 comprises a roller-bearing mounted steel cylinder thattamps the heated feedstock 111 into the heated workpiece 106.

Controller 109 comprises the hardware and software necessary to directrobot 103, build plate support 104, and deposition head 107 in order tofabricate the article of manufacture.

Feedstock reel 110 is a circular reel that stores 1000 meters offeedstock 111 and feeds that feedstock to deposition head 107 and thatmaintains a constant tension on feedstock 111. Feedstock 111 is a carbonfiber-reinforced thermoplastic filament or tape, which is commonlycalled “pre-preg.” Accumulator 112 takes feedstock 111 from feedstockreel 110 and provides it to deposition head 107 with the correct tensionfor depositing.

Optical instrument 161 is hardware that takes high-energy light fromoptical cable 151 and outputs laser beam 171, which illuminates andheats those portions of feedstock 111 and workpiece 106 that are withinirradiated region 271. Laser 141 is a high-energy laser whose outputpower is controlled by controller 109, via laser control cable 191.Because controller 109 controls robot 103 and the speed at whichfeedstock 111 is deposited, controller 109 knows how quickly or slowlyeach unit-length of feedstock 111 must be heated and adjusts laser 141accordingly. When the feedstock is deposited quickly, laser 141 is setto higher power so that feedstock 111 and workpiece 106 can be heatedquickly. In contrast, when feedstock 111 is deposited more slowly, laser141 is set to lower power, and when deposition stops laser 141 is turnedoff. Optical cable 151 is a glass fiber for carrying the light fromlaser 141 to optical instrument 161 with substantially no loss.

Nip line segment 281 is that line segment on the circumferential surfaceof tamping tool 108 where the compressive force on feedstock 111 fromtamping tool 108 and workpiece 106 is at a maximum. Pinch line segment282 is that line segment on the circumferential surface of tamping tool108 where the compressive force on feedstock 111 from tamping tool 108and workpiece 106 first substantially constrains any movement offeedstock 111 parallel to the axis of tamping tool 108.

Deposition path 291 depicts the location on workpiece 106 wherefeedstock 111 is next to be deposited.

In this context, the process of fabricating articles of manufacture withsegments of fiber-reinforced thermoplastic feedstock presents manychallenges.

SUMMARY OF THE INVENTION

Some embodiments of the present invention art are capable of weldingfeedstock to a workpiece without some of the costs and disadvantages fordoing so in the prior art. The nature of these costs and disadvantagesbecomes clear upon close examination of additive manufacturing system100, as presented above and in FIGS. 1, 2 a, 2 b, and 3.

The job of laser beam 171 is to heat each segment of feedstock 111—andthe corresponding portion of workpiece 106 to which it is to bewelded—to a very narrow temperature range above their resin softeningpoint. If the temperature of either is too low, then the weld will bedefective, and if the temperature of either is too high, then it couldburn or melt.

In the prior art, laser beam 171 heats both workpiece 106 and feedstock111 at the same time, in the same manner, and with the beam's energyevenly split between them. Given that both workpiece 106 and feedstock111 comprise the same material and must be heated to the sametemperature, the use of laser beam 171 to heat them both appears to bereasonable. In practice, however, it fails to produce quality welds, andon close examination, the reason why is clear: the task of heating theworkpiece is, in general, far more complex and variable than the task ofheating the feedstock.

The geometry and composition of each unit-length of feedstock 111 isapproximately uniform, and, therefore, each unit-length of feedstock 111has approximately the same surface area, heat capacity, and thermalconductivity as every other segment. As long as the initial temperatureof each segment is the same, then the same amount of heat energy isneeded to heat each segment to its resin softening point.

In contrast, the geometry and fiber orientation of each portion ofworkpiece 106 varies, and, therefore, different portions of workpiece106 have different surface areas, heat capacities, and thermalconductivities. As a result, different portions of workpiece 106 requiredifferent amounts of heat energy to heat them to their resin softeningpoint.

Furthermore, laser beam 271 needs to heat those portions of workpiece106 along deposition path 291. When deposition path 291 is straight,laser beam 271 heats the correct portions, but when deposition path 291twists and turns—as shown in FIG. 2b —laser beam 271 does not heat thecorrect portions.

And still furthermore, the angle of incidence of laser beam 271 onfeedstock 111 is generally consistent, which causes each unit-length offeedstock to absorb the same amount of heat energy per unit-time. Incontrast, the angle of incidence of laser beam 271 on workpiece 106 isinconsistent because of variations in the contour of workpiece 106.This, in turn, causes:

-   -   (i) the irradiance of laser beam 171 at each unit-area on        workpiece 106 to vary, and    -   (ii) the amount of light that is reflected off of workpiece 106        to vary, and    -   (iii) the amount of light that is refracted into—and absorbed        by—workpiece 106 to vary, and    -   (iv) different unit-areas of workpiece 106 to absorb different        amounts of heat energy per unit-time.

To address these and other issues, the first illustrative embodimentcomprises two lasers. One laser beam is solely dedicated to heating thefeedstock, and the other laser beam is solely dedicated to heating theworkpiece. This is advantageous because it enables one laser beam to bededicated to addressing the particular issues associated with heatingthe feedstock and one laser beam to be dedicated to addressing theparticular issues associated with heating the workpiece. Furthermore,the total cost for the two less-powerful lasers can be less than thecost of laser 141 in the prior art.

In accordance with the first illustrative embodiment, each laserbeam—and its associated optical instrument—is independently-controlledto ensure that each segment of feedstock and each portion of theworkpiece are properly heated. For example, and without limitation, thefirst illustrative embodiment employs feedforward, a variety of sensors,and feedback to continually:

-   -   (i) adjust the average power of each laser during each        time-interval, and    -   (ii) steer the workpiece laser beam along the deposition path,        and    -   (iii) adjust the irradiance and angle of incidence of each laser        beam to compensate for changes in the contour of the workpiece        and other factors,        to ensure that each segment of feedstock and each portion of the        workpiece are properly heated, tamped, and welded.

The second illustrative embodiment comprises four lasers. Two laserbeams are solely dedicated to heating the feedstock, and the other twolaser beams are solely dedicated to heating the workpiece. This isadvantageous because it enables two laser beams to cooperate inaddressing the particular issues associated with heating the feedstockand two laser beams to cooperate in addressing the particular issuesassociated with heating the workpiece. Furthermore, the total cost forthe four lasers can be less than the cost of the two lasers in the firstillustrative embodiment.

The second illustrative embodiment is advantageous over the firstillustrative embodiment because the use of four laser beams enablesfine-tuning of the temperature of the feedstock and the workpieceimmediately prior to deposition and tamping. Furthermore, the use offour laser beams is advantageous when the rate of deposition is high(e.g., >100 mm/sec), highly non-uniform, and when the deposition pathcomprises many twists and turns.

The second illustrative embodiment uses one optical cable to carry eachlaser beam from its laser to its associated optical instrument on thedeposition head. Because there are four laser beams, there are fouroptical cables. The third illustrative embodiment adds the means tocarry all of the four laser beams to the deposition head via only oneoptical cable. This is advantageous because it enables the depositionhead to be lighter and more compact.

These and other advantages of the illustrative embodiments will beapparent in the disclosure below and in the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an illustration of additive manufacturing system 100 inthe prior art, which system fabricates articles of manufacture bysuccessively depositing segments of fiber-reinforced thermoplasticfeedstock (e.g., filament, tape, etc.) on top of one another.

FIG. 2a depicts a close-up of workpiece 106, deposition head 107,tamping tool 108, feedstock 111, optical cable 151, optical instrument161, and laser beam 171, as depicted in FIG. 1.

FIG. 2b depicts a close-up of workpiece 106, deposition head 107,tamping tool 108, and feedstock 111 along cross-section AA-AA, asdepicted in FIG. 2 a.

FIG. 3 depicts a schematic diagram of the heating architecture foradditive manufacturing system 100.

FIG. 4 depicts an illustration of additive manufacturing system 400 inaccordance with the first illustrative embodiment of the presentinvention.

FIG. 5a depicts a close-up of workpiece 406, deposition head 407,tamping tool 408, feedstock 411, sensor array 415, optical instrument461, optical instrument 462, optical cable 451, optical cable 452,sensor cable 454, laser beam 471, laser beam 472, feedstock region571-1, feedstock region 571-2, feedstock region 571-3, workpiece region572-1, workpiece region 572-2, workpiece region 572-3, nip line segment581, and pinch line segment 582, interrelated as shown.

FIG. 5b depicts a close-up of workpiece 406 in which deposition path 591curves to the right (from the perspective of deposition head 407).

FIG. 6 depicts a close-up of workpiece 406 in which deposition path 591curves to the left (from the perspective of deposition head 407).

FIG. 7 depicts a schematic diagram of the heating and sensorarchitecture for additive manufacturing system 400, which irradiates andheats feedstock 411 and workpiece 406 and measures the temperature offeedstock 411 and workpiece 406.

FIG. 8 depicts a schematic diagram of the sensor and controlarchitecture for that portion of additive manufacturing system 400 thatirradiates and heats feedstock 411 and workpiece 406.

FIG. 9 depicts a flowchart of the tasks performed by additivemanufacturing system 400. Because additive manufacturing system 400concurrently performs tasks on different segments of feedstock 411 anddifferent portions of workpiece 406, the tasks depicted in FIG. 9 areconcurrent.

FIG. 10 depicts a flowchart of the details of task 907—adjusting opticalinstrument 461 and optical instrument 462, as directed by controller409.

FIG. 11 depicts a flowchart of the relative timing of the tasksperformed on segment m of feedstock 411 and on portion n of workpiece406, wherein m and n are integers. In accordance with the firstillustrative embodiment segment m of feedstock 411 is deposited andtamped onto portion n of workpiece 406.

FIG. 12 depicts an illustration of additive manufacturing system 1200 inaccordance with the second illustrative embodiment of the presentinvention.

FIG. 13a depicts a close-up of workpiece 1206, deposition head 1207,tamping tool 1208, feedstock 1211, sensor array 1215, optical instrument1260, optical instrument 1261, optical instrument 1262, opticalinstrument 1263, optical cable 1250, optical cable 1251, optical cable1252, optical cable 1253, sensor cable 1254, laser beam 1270, laser beam1271, laser beam 1272, laser beam 1273, feedstock region 1371-1,feedstock region 1371-2, feedstock region 1371-3, workpiece region1372-1, workpiece region 1372-2, workpiece region 1372-3, nip linesegment 1381, and pinch line segment 1382, interrelated as shown.

FIG. 13b depicts a close-up of workpiece 1206 in which deposition path1391 curves to the right (from the perspective of deposition head 1207).

FIG. 14 depicts a close-up of workpiece 1206 in which deposition path1391 curves to the left (from the perspective of deposition head 1207).

FIG. 15 depicts a schematic diagram of the heating and sensorarchitecture for additive manufacturing system 1200, which irradiatesand heats feedstock 1211 and workpiece 1206 and measures the temperatureof feedstock 1211, workpiece 1206, and tamping tool 1208.

FIG. 16 depicts a schematic diagram of the sensor and controlarchitecture for that portion of additive manufacturing system 1200 thatirradiates and heats feedstock 1211 and workpiece 1206.

FIG. 17 depicts a flowchart of the tasks performed by additivemanufacturing system 1200. Because additive manufacturing system 1200concurrently performs tasks on different segments of feedstock 1211 anddifferent portions of workpiece 1206, the tasks depicted in FIG. 17 areconcurrent.

FIG. 18 depicts a flowchart of the details of task 1707—adjustingoptical instruments as directed by controller 1209.

FIG. 19 depicts a flowchart of the details of task 1801—adjustingoptical instrument 1260.

FIG. 20 depicts a flowchart of the details of task 1802—adjustingoptical instrument 1261.

FIG. 21 depicts a flowchart of the details of task 1803—adjustingoptical instrument 1262.

FIG. 22 depicts a flowchart of the details of task 1804—adjustingoptical instrument 1263.

FIG. 23 depicts a flowchart of the relative timing of the tasksperformed on segment m of feedstock 1211 and on portion n of workpiece1206, wherein m and n are integers. In accordance with the secondillustrative embodiment segment m of feedstock 1211 is deposited andtamped onto portion n of workpiece 1206.

FIG. 24 depicts an illustration of additive manufacturing system 2400 inaccordance with the third illustrative embodiment of the presentinvention.

FIG. 25 depicts a close-up of workpiece 1206, deposition head 1207,tamping tool 1208, feedstock 1211, sensor array 1215, optical instrument1260, optical instrument 1261, optical instrument 1262, opticalinstrument 1263, optical cable 2454, sensor cable 1254, laser beam 1270,laser beam 1271, laser beam 1272, laser beam 1273, feedstock region1371-1, feedstock region 1371-2, feedstock region 1371-3, workpieceregion 1372-1, workpiece region 1372-2, workpiece region 1372-3, nipline segment 1381, and pinch line segment 1382, beam splitter 2461, beamsplitter 2462, and beam splitter 2463, interrelated as shown.

FIG. 26 depicts a schematic diagram of the heating and sensorarchitecture for additive manufacturing system 2400, which irradiatesand heats feedstock 1211 and workpiece 1206 and measures the temperatureof feedstock 1211, workpiece 1206, and tamping tool 1208.

DEFINITIONS

Irradiance—For the purposes of this specification, the term “irradiance”is defined as the radiant flux received by a surface per unit-area. TheSI unit of irradiance is the Watt per meter².

Nip line segment—For the purposes of this specification, a “nip linesegment” on a tamping tool is defined as line segment on thecircumferential surface of the tamping tool where the tamping toolexerts the maximum radial force on a feedstock.

Pinch line segment—for the purposes of this specification, a “pinch linesegment” on a tamping tool is defined as the line segment on thecircumferential surface of the tamping tool where the tamping tool firstpinches a unit-length of feedstock between the tamping tool and theworkpiece so that any movement of the feedstock parallel to therotational axis of the tamping tool is substantially constrained.

Printer—For the purposes of this specification, a “printer” is definedas an additive manufacturing system or an additive and subtractivemanufacturing system.

Printing—For the purposes of this specification, the infinitive “toprint” and its inflected forms is defined as to fabricate. The act offabrication is widely called “printing” in the field of additivemanufacturing.

Resin Softening Point—For the purposes of this specification, the phrase“resin softening point” is defined as the temperature at which the resinsoftens beyond some arbitrary softness.

Workpiece—For the purposes of this specification, a “workpiece” isdefined as an inchoate article of manufacture.

DETAILED DESCRIPTION

FIG. 4 depicts an illustration of additive manufacturing system 400 inaccordance with the first illustrative embodiment of the presentinvention. Additive manufacturing system 400 fabricates an article ofmanufacture by successively depositing segments of fiber-reinforcedthermoplastic feedstock (e.g., filament, tape, etc.) onto a workpieceuntil the article of manufacture is complete.

Additive manufacturing system 400 comprises: platform 401, robot mount402, robot 403, build plate support 404, build plate 405, workpiece 406,deposition head 407, tamping tool 408, controller 409, feedstock reel410, feedstock 411, accumulator 412, force gauge 413, sensor array 415,feedstock laser 441, workpiece laser 442, optical cable 451, opticalcable 452, sensor cable 454, optical instrument 461, optical instrument462, laser beam 471, laser beam 472, feedstock laser control cable 491,and workpiece laser control cable 492, interrelated as shown.

FIG. 5a depicts a close-up of workpiece 406, deposition head 407,tamping tool 408, feedstock 411, sensor array 415, optical instrument461, optical instrument 462, optical cable 451, optical cable 452,sensor cable 454, laser beam 471, laser beam 472, feedstock region571-1, feedstock region 571-2, feedstock region 571-3, workpiece region572-1, workpiece region 572-2, workpiece region 572-3, nip line segment581, and pinch line segment 582, interrelated as shown.

FIG. 5b depicts a close-up of workpiece 406, deposition head 407,tamping tool 408, feedstock 411, feedstock region 571-1, feedstockregion 571-2, feedstock region 571-3, workpiece region 572-1, workpieceregion 572-2, workpiece region 572-3, pinch line segment 582, anddeposition path 591 all as seen along cross-section BB-BB as depicted inFIG. 5 a.

FIG. 6 depicts a close-up of workpiece 406, deposition head 407, tampingtool 408, feedstock 411, feedstock region 571-1, feedstock region 571-2,feedstock region 571-3, workpiece region 572-1, workpiece region 572-2,workpiece region 572-3, pinch line segment 582, and deposition path 591,all as seen along cross-section BB-BB as depicted in FIG. 5 a.

FIG. 6 differs from FIG. 5a in that the curvature of deposition path 591in FIG. 5a curves to the right (from the perspective of deposition head407) whereas deposition path 591 in FIG. 6 curves to the left. This isbecause additive manufacturing system 400 steers laser beam 472,workpiece region 572-1, workpiece region 572-2, and workpiece region572-3 onto deposition path 591 as deposition path 591 meanders onworkpiece 406.

Platform 401 is a rigid metal structure and is identical to platform 101in the prior art. Platform 401 ensures that the relative spatialrelationship of robot mount 402, robot 403, deposition head 407, tampingtool 408, optical instrument 461, optical instrument 462, and sensorarray 415 are maintained and known with respect to build-plate support404, build plate 405, workpiece 406, and deposition path 591. It will beclear to those skilled in the art how to make and use platform 401.

Robot mount 402 is a rigid, massive, and stable support for robot 403and is identical to robot mount 102 in the prior art. The purpose ofrobot mount 402 is to provide ballast and inertial stability for robot403. It will be clear to those skilled in the art how to make and userobot mount 402.

Robot 403 is a six-axis articulated mechanical arm that supportsdeposition head 407, tamping tool 408, optical instrument 461, opticalinstrument 462, sensor array 415, optical cable 451, optical cable 452,and sensor cable 454. Robot 403 is identical to robot 103 in the priorart. It will be clear to those skilled in the art, however, afterreading this disclosure, how to make and use alternative embodiments ofthe present invention in which a different type of robot (e.g., acartesian robot, a cylindrical robot, a SCARA, a delta robot, etc.) isused. A non-limiting example of robot 403 is the IRB 4600 robot offeredby ABB. The motion of robot 403 is under the direction of controller409, and robot 403 is capable of depositing feedstock 411 at anylocation on workpiece 406 and in any one-, two-, or three-dimensionalcurve. It will be clear to those skilled in the art how to make and userobot 403.

Build plate support 404 is a rigid, massive, and stable support forbuild plate 405 and workpiece 406 and is identical to build platesupport 104 in the prior art. The purpose of build plate support 404 isto provide ballast and inertial stability for build plate 405 and alsoto provide a mechanism for rotating build plate 405 around an axis thatis normal to the X-Y plane. To wit, build plate support 404 comprises astepper motor—under the direction of controller 409—that is capable ofrotating build plate 405 (and, consequently workpiece 406) around anaxis that is normal to the X-Y plane. It will be clear to those skilledin the art how to make and use build plate support 404.

Build plate 405 is a rigid aluminum-alloy support and is described indetail in U.S. patent application Ser. No. 16/792,156, entitled“Thermoplastic Mold with Implicit Registration,” filed on Feb. 14, 2020,and incorporated by reference for the purpose of describing build plate405. The purpose of build plate 405 is to provide support for workpiece406 (and a mold with a tunably adhesive surface for workpiece 406). U.S.patent application Ser. No. 16/792,150, entitled “Thermoplastic Moldwith Tunable Adhesion,” filed on Feb. 14, 2020 is also incorporated byreference for the purpose of describing the interface between buildplate 405 and workpiece 4066. It will be clear to those skilled in theart how to make and use build plate 405 after reading this disclosureand the incorporated patent applications.

Workpiece 406 comprises a plurality of segments of feedstock 411 thathave been successively deposited and welded together in a desiredgeometry to form the inchoate article of manufacture. Workpiece 406 issteadfastly affixed to build plate 405 so that workpiece 406 cannot moveor rotate independently of build plate 405.

Deposition head 407 is the end effector of robot 403 and comprises:

-   -   (i) a feedstock guide that feeds feedstock 411 into position for        heating, tamping, and welding to workpiece 406. The feedstock        guide is omitted from the figures for clarity but is described        in U.S. Pat. No. 10,076,870, entitled “Filament Guide,” issued        on Sep. 18, 2018, which is incorporated by reference.    -   (ii) tamping tool 408, which first pinches and then tamps each        segment of feedstock 411 onto the corresponding portion of        workpiece 406.    -   (iii) force gauge 413 that continually measures the force of        tamping tool 408 on feedstock 411 at nip line segment 581 and        reports those measurements back to controller 409 via sensor        cable 454.    -   (iv) a feedstock cutter—under the direction of controller        409—that periodically or sporadically cuts feedstock 411. The        feedstock cutter is omitted from the figures for clarity but is        described in U.S. patent application Ser. No. 16/023,197,        entitled “Filament Cutter,” filed on Jun. 29, 2018, which is        incorporated by reference.    -   (v) optical instrument 461, which takes laser beam 471 from        optical cable 451, and—under the direction of controller        409—conditions laser beam 471 and directs it onto feedstock        region 571-2.    -   (vi) optical instrument 462, which takes laser beam 472 from        optical cable 452, and—under the direction of controller        409—conditions laser beam 472 and directs it onto workpiece        region 572-2.    -   (vii) sensor array 415, which measures the temperature of        feedstock region 571-2, workpiece region 572-2, and tamping tool        408 and reports those measurements to controller 409 via sensor        cable 454.    -   (viii) structural support for optical instrument 461, optical        instrument 462, and sensor array 415 and that maintains the        relative spatial location and position of the feedstock guide,        tamping tool 408, pinch line segment 582, the cutter, optical        instrument 461, optical instrument 462, and sensor array 415.        The structural support is omitted from the figures for clarity        but it will be clear to those skilled in the art, after reading        this disclosure, how to make and use the structural support.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use deposition head 407.

Tamping tool 408 comprises a roller-bearing mounted steel cylinder(roller) whose tangential speed equals the linear speed of the feedstockadjacent to the roller (i.e., tamping tool 408 rotates freely and thereis substantially no friction between tamping tool 408 and feedstock 411.It will be clear to those skilled in the art how to make and use tampingtool 408.

The following patent applications disclose designs for tamping tool 408which are alternatives to the roller-bearing mounted steel cylinder:

-   (i) U.S. patent application Ser. No. 15/959,213, entitled    “Variable-Contour Compaction Press,” filed on Apr. 21, 2018; and-   (ii) U.S. patent application Ser. No. 15/959,214, entitled    “Variable-Contour Compaction Roller,” filed on Apr. 21, 2018; and-   (iii) U.S. patent application Ser. No. 15/959,215, entitled    “Self-Cleaning Variable-Contour Compaction Press,” filed on Apr. 21,    2018;    each of which is incorporated by reference.

Controller 409 comprises the hardware and software necessary to controlall aspects of fabricating the article of manufacture, including, butnot limited to:

(i) robot 403 (which includes the location and motion of tamping tool408), and

(ii) build plate support 404, and

(iii) the feedstock cutter, and

(iv) feedstock laser 441, and

(v) workpiece laser 442, and

(vi) optical instrument 461, and

(vii) optical instrument 462, and

(viii) accumulator 412.

To accomplish this controller 409 relies on a combination of feedforwardand feedback, as described in detail below and in the accompanyingdrawings. It will be clear to those skilled in the art, after readingthis disclosure, how to make and use controller 409.

Feedstock reel 410 is a circular reel that stores 1000 meters offeedstock 411. Feedstock real 410 feeds feedstock 411 to accumulator412. It will be clear to those skilled in the art how to make and usefeedstock reel 410.

Feedstock 411 is a carbon fiber-reinforced thermoplastic filament, whichis commonly called “pre-preg.” It will be clear to those skilled in theart, however, after reading this disclosure, how to make and usealternative embodiments of the present invention in which the feedstockis a fiber-reinforced pre-preg tape—woven or uni-directional—that isimpregnated with thermoplastic resin.

Feedstock 411 comprises cylindrical towpreg of contiguous 12K carbonfiber that is impregnated with thermoplastic resin. The cross-section iscircular and has a diameter of 1000 μm. It will be clear to thoseskilled in the art, however, after reading this disclosure, how to makeand use alternative embodiments of the present invention in which thecross-section of the filament is a quadrilateral (e.g., a square, arectangle, a rhombus, a trapezoid, a kite, a parallelogram, etc.).Furthermore, it will be clear to those skilled in the art how to makeand use alternative embodiments of the present invention in whichfeedstock 411 comprises a different number of fibers (e.g., 1K, 3K, 6K,24K, etc.). And still furthermore, it will be clear to those skilled inthe art how to make and use alternative embodiments of the presentinvention in which the fibers in feedstock 111 are made of a differentmaterial (e.g., fiberglass, aramid, carbon nanotubes, etc.).

In accordance with the first illustrative embodiment, feedstock 411comprises continuous carbon fiber, but it will be clear to those skilledin the art how to make and use alternative embodiments of the presentinvention in which feedstock 411 comprises chopped or milled fiber.

In accordance with the first illustrative embodiments, the thermoplasticin feedstock 411 is, in general, a semi-crystalline polymer and, inparticular, the polyaryletherketone (PAEK) known as polyetherketone(PEK). In accordance with some alternative embodiments of the presentinvention, the semi-crystalline material is the polyaryletherketone(PAEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK),polyetheretherketoneketone (PEEKK), or polyetherketoneetherketoneketone(PEKEKK). As those who are skilled in the art will appreciate afterreading this specification, the disclosed annealing process, as itpertains to a semi-crystalline polymer in general, takes place at atemperature that is above the glass transition temperature Tg.

In accordance with some alternative embodiments of the presentinvention, the semi-crystalline polymer is not a polyaryletherketone(PAEK) but another semi-crystalline thermoplastic (e.g., polyamide (PA),polybutylene terephthalate (PBT), poly(p-phenylene sulfide) (PPS), etc.)or a mixture of a semi-crystalline polymer and an amorphous polymer.

When feedstock 411 comprises a blend of an amorphous polymer with asemi-crystalline polymer, the semi-crystalline polymer can one of theaforementioned materials and the amorphous polymer can be apolyarylsulfone, such as polysulfone (PSU), polyethersulfone (PESU),polyphenylsulfone (PPSU), polyethersulfone (PES), or polyetherimide(PEI). In some additional embodiments, the amorphous polymer can be, forexample and without limitation, polyphenylene oxides (PPOs),acrylonitrile butadiene styrene (ABS), methyl methacrylate acrylonitrilebutadiene styrene copolymer (ABSi), polystyrene (PS), or polycarbonate(PC). As those who are skilled in the art will appreciate after readingthis specification, the disclosed annealing process, as it pertains to ablend of an amorphous polymer with a semi-crystalline polymer, takesplace generally at a lower temperature than a semi-crystalline polymerwith the same glass transition temperature; in some cases, the annealingprocess can take place at a temperature slightly below the glasstransition temperature.

When the feedstock comprises a blend of an amorphous polymer with asemi-crystalline polymer, the weight ratio of semi-crystalline materialto amorphous material can be in the range of about 50:50 to about 95:05,inclusive, or about 50:50 to about 90:10, inclusive. Preferably, theweight ratio of semi-crystalline material to amorphous material in theblend is between 60:40 and 80:20, inclusive. The ratio selected for anyparticular application may vary primarily as a function of the materialsused and the properties desired for the printed article.

In some alternative embodiment of the present invention, the feedstockcomprises a metal. For example, and without limitation, the feedstockcan be a wire comprising stainless steel, Inconel (nickel/chrome),titanium, aluminum, cobalt chrome, copper, bronze, iron, precious metals(e.g., platinum, gold, silver, etc.).

In accordance with the first illustrative embodiment, the thermoplasticis infused with carbon nano-particles, the purpose of which is two-fold.First, the carbon nano-particles facilitate the absorption of radiantheat from laser beam 471 and laser beam 472. Second, the carbonnano-particles effectively change the reactance of the thermoplastic,which makes the completed article of manufacture more conducive toelectro-static powder coating.

Accumulator 412 takes feedstock 411 from feedstock reel 410 and providesit to deposition head 407 with the correct tension for depositing.Accumulator 112 is described in detail by U.S. patent application Ser.No. 16/023,210, entitled “Filament Accumulator or Tensioning Assembly,”filed Jun. 29, 2018, and which is incorporated by reference.

Sensor array 415 is a thermal camera that is capable of simultaneouslymeasuring the temperature of:

(i) feedstock region 571-1, and

(ii) feedstock region 571-2, and

(iii) feedstock region 571-3, and

(iv) workpiece region 572-1, and

(v) workpiece region 572-2, and

(vi) workpiece region 572-3, and

(vii) tamping tool 408,

sixty (60) times per second and reporting those measurements tocontroller 409 via sensor cable 454. In accordance with the firstillustrative embodiment, sensor array 415 is a FLIR A35 thermal camera,but it will be clear to those skilled in the art, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which sensor array 415 comprises different hardware.

Force Gauge 413—is a mechanical strain gauge that continually measuresthe force of tamping tool 408 on feedstock 411 at nip line segment 581and reports those measurements back to controller 409 via sensor cable454. It will be clear to those skilled in the art how to make and useforce gauge 413.

Feedstock laser 441 is a variable-power continuous-wave laser thatgenerates laser beam 471 and conveys it to optical instrument 461 viaoptical cable 451. In accordance with the first illustrative embodiment,feedstock laser 441 is directed by controller 409 to generate laser beam471 with a specific average power over a given time-interval. Inaccordance with the first illustrative embodiment, laser beam 471 ischaracterized by a wavelength λ=980 nm and has a maximum power output of400 Watts.

In accordance with the illustrative embodiment, feedstock laser 441 is acontinuous-wave laser. It will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention that use a pulsed laser. In anycase, it will be clear to those skilled in the art how to make and usefeedstock laser 441.

Workpiece laser 442 is a variable-power continuous-wave laser thatgenerates laser beam 472 and conveys it to optical instrument 462 viaoptical cable 452. In accordance with the first illustrative embodiment,workpiece laser 442 is directed by controller 409 to generate laser beam472 with a specific average power over a given time-interval. Inaccordance with the first illustrative embodiment, laser beam 472 ischaracterized by a wavelength λ=980 nm and has a maximum power output of400 Watts.

In accordance with the illustrative embodiment, workpiece laser 442 is acontinuous-wave laser. It will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention that use a pulsed laser. In anycase, it will be clear to those skilled in the art how to make and useworkpiece laser 442.

In accordance with the first illustrative embodiment, feedstock laser441 and workpiece laser 442 are identical and generate laser beamscharacterized by the same wavelength. It will be clear to those skilledin the art, however, after reading this disclosure, how to make and usealternative embodiments of the present invention in which the lasers:

(i) are not identical, or

(i) generate laser beams characterized by different wavelengths, or

(iii) have different maximum power output, or

(iv) any combination of i, ii, and iii.

Optical cable 451 is a glass fiber, in well-known fashion, that carrieslaser beam 471 from feedstock laser 441 to optical instrument 461 withsubstantially no loss. It will be clear to those skilled in the art howto make and use optical cable 451.

Optical cable 452 is a glass fiber, in well-known fashion, that carriesthe laser beam 472 from workpiece laser 442 to optical instrument 462with substantially no loss. It will be clear to those skilled in the arthow to make and use optical cable 452.

Sensor cable 454 is an electrical cable, in well-known fashion, thatcarries the measurements from sensor array 415 to controller 409. Itwill be clear to those skilled in the art how to make and use sensorcable 454.

Optical instrument 461 is an optomechanical machine that comprisesoptics and actuators that receive laser beam 471 from feedstock laser441, via optical cable 451, conditions it under the direction ofcontroller 409, and directs it onto the segment of feedstock 411 that iswithin feedstock region 571-2. In accordance with the first illustrativeembodiment, optical instrument 461 comprises:

-   -   (i) an actuator and an optic that, under the direction of        controller 409, adjusts the length of the segment of feedstock        411 that is irradiated and heated by laser beam 471 (i.e.,        adjusts the length of feedstock region 571-2), and    -   (ii) an actuator and an optic that, under the direction of        controller 409, adjusts the distance between pinch line segment        582 and laser beam 471 (i.e., adjusts the distance between pinch        line segment 582 and feedstock region 571-2), and    -   (iii) an actuator and an optic that, under the direction of        controller 409, adjusts the irradiance within each unit-area of        laser beam 471 on feedstock 411, and    -   (iv) an actuator and an optic that, under the direction of        controller 409, adjusts the angle of incidence of laser beam 471        on feedstock 411.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use optical instrument 461.

Optical instrument 462 is an optomechanical machine that comprisesoptics and actuators that receive laser beam 472 from workpiece laser442, via optical cable 452, conditions it, and directs it onto theportion of workpiece 406 that is within workpiece region 572-2, allunder the direction of controller 409. In accordance with the firstillustrative embodiment, optical instrument 461 comprises:

-   -   (i) an actuator and an optic that, under the direction of        controller 409, adjusts the length of the portion of workpiece        406 that is irradiated and heated by laser beam 472 (i.e.,        adjusts the length of workpiece region 572-2), and    -   (ii) an actuator and an optic that, under the direction of        controller 409, adjusts the distance between pinch line segment        582 and laser beam 472 (i.e., adjusts the distance between pinch        line segment 582 and workpiece region 572-2), and    -   (iii) an actuator and an optic that, under the direction of        controller 409, adjusts the irradiance within each unit-area of        laser beam 472 on workpiece 406, and    -   (iv) an actuator and an optic that, under the direction of        controller 409, adjusts the angle of incidence of laser beam 472        on workpiece 406, and    -   (v) an actuator that steers laser beam 472 onto deposition path        591.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use optical instrument 462.

Feedstock laser control cable 491 is an electrical cable, in well-knownfashion, that carries instructions from controller 409 to feedstocklaser 441, which instructions control all aspects (e.g., power, etc.) offeedstock laser 441. It will be clear to those skilled in the art how tomake and use feedstock laser control cable 491.

Workpiece laser control cable 492 is an electrical cable, in well-knownfashion, that carries instructions from controller 409 to workpiecelaser 442, which instructions control all aspects (e.g., power, etc.) ofworkpiece laser 442. It will be clear to those skilled in the art how tomake and use feedstock laser control cable 492.

Feedstock region 571-1, feedstock region 571-2, and feedstock region571-3 are three volumes in space through which feedstock 411 passes.

The length of feedstock region 571-1 is defined as the length offeedstock 411 within feedstock region 571-1. In accordance with thefirst illustrative embodiment, the length of feedstock region 571-1 is15 mm, but it will be clear to those skilled in the art, after readingthis disclosure, how to make and use alternative embodiments in whichthe length of feedstock region 571-1 is different.

The length of feedstock region 571-2 is defined as the length offeedstock 411 being irradiated by laser beam 471. In accordance with thefirst illustrative embodiment, the length of feedstock region 571-2 iscontinually adjusted by optical instrument 461, all under the directionof controller 409. In accordance with the first illustrative embodiment,the minimum length of feedstock region 571-2 is 5 mm and the maximumlength is 15 mm, but it will be clear to those skilled in the art, afterreading this disclosure, how to make and use alternative embodiments ofthe present invention in which the minimum and maximum lengths aredifferent.

The length of feedstock region 571-3 is defined as the length offeedstock 411 within feedstock region 571-3. In accordance with thefirst illustrative embodiment, the length of feedstock region 571-3 is10 mm, but it will be clear to those skilled in the art, after readingthis disclosure, how to make and use alternative embodiments in whichthe length of the feedstock region 571-3 is different.

In accordance with the first illustrative embodiment, the distance offeedstock region 571-1 from pinch line segment 582 (as measured alongthe length of feedstock 411) is 55 mm, but it will be clear to thoseskilled in the art, after reading this disclosure, how to make and usealternative embodiments in which the distance is different.

In accordance with the first illustrative embodiment, the distance offeedstock region 571-2 from pinch line segment 582 (as measured alongthe length of feedstock 411) is continually adjusted by opticalinstrument 461, all under the direction of controller 409. In accordancewith the first illustrative embodiment, the minimum distance offeedstock region 571-2 from pinch line segment 582 is 25 mm and themaximum distance is 35 mm, but it will be clear to those skilled in theart, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which the minimum and maximumlengths are different.

In accordance with the first illustrative embodiment, the distance offeedstock region 571-3 from pinch line segment 582 (as measured alongthe length of feedstock 411) is 5 mm but it will be clear to thoseskilled in the art, after reading this disclosure, how to make and usealternative embodiments in which the distance is different.

Workpiece region 572-1, workpiece region 572-2, and workpiece region572-3 are three volumes in space through which deposition path 591passes.

The length of workpiece region 572-1 is defined as the length ofdeposition path 591 within workpiece region 572-1. In accordance withthe first illustrative embodiment, the length of workpiece region 572-1is 15 mm, but it will be clear to those skilled in the art, afterreading this disclosure, how to make and use alternative embodiments inwhich the length of workpiece region 572-1 is different.

The length of workpiece region 572-2 is defined as the length ofdeposition path 591 being irradiated by laser beam 472. In accordancewith the first illustrative embodiment, the length of workpiece region572-2 is continually adjusted by optical instrument 462, all under thedirection of controller 409. In accordance with the first illustrativeembodiment, the minimum length of workpiece region 572-2 is 5 mm and themaximum length is 15 mm, but it will be clear to those skilled in theart, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which the minimum and maximumlengths are different.

The length of workpiece region 572-3 is defined as the length ofdeposition path 591 within workpiece region 572-3. In accordance withthe first illustrative embodiment, the length of workpiece region 572-3is 10 mm, but it will be clear to those skilled in the art, afterreading this disclosure, how to make and use alternative embodiments inwhich the length of the workpiece region 572-3 is different.

In accordance with the first illustrative embodiment, the distance ofworkpiece region 572-1 from pinch line segment 582 (as measured alongthe length of deposition path 591) is 55 mm, but it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments in which the distance is different.

In accordance with the first illustrative embodiment, the distance ofworkpiece region 572-2 from pinch line segment 582 (as measured alongthe length of deposition path 591) is continually adjusted by opticalinstrument 462, all under the direction of controller 409. In accordancewith the first illustrative embodiment, the minimum distance ofworkpiece region 572-2 from pinch line segment 582 is 25 mm and themaximum distance is 35 mm, but it will be clear to those skilled in theart, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which the minimum and maximumlengths are different.

Nip line segment 581 is the line segment on the circumferential surfaceof tamping tool 408 where tamping tool 408 exerts the maximum radialforce on feedstock 411.

Pinch line segment 582 is the line segment on the circumferentialsurface of tamping tool 408 where tamping tool 408 first pinches aunit-length of feedstock 411 between tamping tool 408 and workpiece 406so that any movement of feedstock 411 parallel to the rotational axis oftamping tool 408 is substantially constrained.

Deposition path 591 is a line on the surface of workpiece 406 wherefeedstock 411 is to be deposited and tamped. In FIG. 5b , depositionpath 591 curves to the left. In contrast, in FIG. 6, deposition path 591curves to the right.

FIG. 7 depicts a schematic diagram of the heating and sensorarchitecture for additive manufacturing system 400, which irradiates andheats feedstock 411 and workpiece 406 and measures the temperature offeedstock 411, workpiece 406, and tamping tool 408.

As shown in FIG. 7, feedstock laser 441 provides laser beam 471 tooptical instrument 461 via optical cable 451 in well-known fashion, andworkpiece laser 442 provides laser beam 472 to optical instrument 462via optical cable 452.

Under the direction of controller 409, optical instrument 461 irradiatesand heats the segment of feedstock that is within feedstock region571-2, and optical instrument 462 irradiates and heats the portion ofworkpiece 406 that is within workpiece region 572-2.

Thermal sensor 771-1 periodically measures the temperature of thesegment of feedstock that is within feedstock region 571-1 and reportsthose measurements back to controller 409. Thermal sensor 771-2periodically measures the temperature of the segment of feedstock thatis within feedstock region 571-2 and reports those measurements back tocontroller 409. Thermal sensor 771-3 periodically measures thetemperature of the segment of feedstock that is within feedstock region571-3 and reports those measurements back to controller 409.

Thermal sensor 772-1 periodically measures the temperature of thatportion of workpiece 406 that is within workpiece region 572-1 andreports those measurements back to controller 409. Thermal sensor 772-2periodically measures the temperature of that portion of workpiece 406that is within workpiece region 572-2 and reports those measurementsback to controller 409. Thermal sensor 772-3 periodically measures thetemperature of that portion of workpiece 406 that is within workpieceregion 572-3 and reports those measurements back to controller 409.

Thermal sensor 773 periodically measures the temperature of tamping tool408 and reports those measurements back to controller 409.

Although the first illustrative embodiment measures the temperature ofthree segments of feedstock 411, it will be clear to those skilled inthe art, after reading this disclosure, how to make and use alternativeembodiments of the present invention that measure any number (e.g.,four, five, six, eight, ten, twelve, etc.) of segments. Although thefirst illustrative embodiment measures the temperature of three portionsof workpiece 406, it will be clear to those skilled in the art, afterreading this disclosure, how to make and use alternative embodiments ofthe present invention that measure any number (e.g., four, five, six,eight, ten, twelve, etc.) of portions.

In accordance with the first illustrative embodiment, the temperaturemeasurements are made periodically at sixty (60) times per second, butit will be clear to those skilled in the art, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention that make periodic measurements at a different rate or thatmake measurements aperiodically or sporadically.

FIG. 8 depicts a schematic diagram of the sensor and controlarchitecture for that portion of additive manufacturing system 400 thatirradiates and heats feedstock 411 and workpiece 406.

In accordance with the first illustrative embodiment, controller 409uses a combination of feedforward and feedback to continually direct:

-   -   (i) feedstock laser 441 to adjust the average power of laser        beam 471 on the segment of feedstock that is within feedstock        region 571-2, and    -   (ii) optical instrument 461 to adjust the length of feedstock        region 571-2, and    -   (iii) optical instrument 461 to adjust the distance between        pinch line segment 582 and feedstock region 571-2, and    -   (iv) optical instrument 461 to adjust the irradiance of laser        beam 471 on the segment of feedstock 411 within feedstock region        571-2, and    -   (v) optical instrument 461 to adjust the angle of incidence of        laser beam 471 on the segment of feedstock 411 within feedstock        region 571-2, and    -   (vi) workpiece laser 442 to adjust the average power of laser        beam 472 on the portion of workpiece that is within workpiece        region 572-2, and    -   (vii) optical instrument 462 to adjust the length of workpiece        region 572-2, and    -   (viii) optical instrument 462 to adjust the distance between        pinch line segment 582 and workpiece region 572-2, and    -   (ix) optical instrument 462 to adjust the irradiance of laser        beam 472 on the portion of workpiece 406 within workpiece region        572-2, and    -   (x) optical instrument 462 to adjust the angle of incidence of        laser beam 472 on the portion of workpiece 406 within workpiece        region 572-2, and    -   (xi) optical instrument 462 to steer laser beam 472 onto        deposition path 591, and    -   (xii) accumulator 412 to feed feedstock 411 to deposition head        407, and    -   (xiii) robot 403 to advance tamping tool 408 to deposit and tamp        feedstock 411 onto workpiece 406, and        based on:    -   (i) knowledge of the toolpath (e.g., G-code, etc.) for the        article of manufacture to be printed (and the geometry of the        workpiece at each time-interval, which can be derived from that        toolpath), and    -   (ii) a thermal model of the feedstock 411, and    -   (iii) a location-specific thermal model of each portion on        workpiece 406 onto which feedstock 411 will be deposited and        tamped (which can be derived from the thermal model of the        feedstock 411 and the geometry of the workpiece at each instant        during fabrication), and    -   (iv) periodic measurements of the temperature of the segment of        feedstock 411 that is within feedstock region 571-1, and    -   (v) periodic measurements of the temperature of the segment of        feedstock 411 that is within feedstock region 571-2, and    -   (vi) periodic measurements of the temperature of the segment of        feedstock 411 that is within feedstock region 571-3, and    -   (vii) periodic measurements of the temperature of that portion        of workpiece that is within workpiece region 572-1, and    -   (viii) periodic measurements of the temperature of that portion        of workpiece that is within workpiece region 572-2, and    -   (ix) periodic measurements of the temperature of that portion of        workpiece that is within workpiece region 572-3, and    -   (x) periodic measurements of the temperature of tamping tool        408, and    -   (xi) periodic measurements of the force of tamping tool 408 on        feedstock 411 at nip line segment 581.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use embodiments of the present        invention that accomplish this, whether with traditional        imperative programming or with an artificial neural network.

With regard to feedforward, controller 409 takes as input:

-   -   (i) the toolpath (e.g., G-code, etc.) for the article of        manufacture to be printed, in well-known fashion, and    -   (ii) a thermal model of the feedstock, which itself is based on,        among other things, the thermal properties of the resin, the        mass of resin per unit-length of feedstock, the profile of the        feedstock (e.g., filament, tape, circular, rectangular, etc.),        the thermal properties of the reinforcing fibers, the number of        fibers per unit-length of feedstock, the mass of the fibers per        unit-length of feedstock, and the length and orientation of the        fibers in the feedstock (e.g., continuous, chopped, medium, ball        milled, etc.),        and generates therefrom:    -   (i) a prediction of whether feedstock 411 will be deposited at a        uniform or non-uniform rate at each instant during the printing        of the article of manufacture (because, for example and without        limitation, the deposition starts and stops, accelerates,        decelerates and occurs uniformly because of turns, contours,        cuts, etc.), and    -   (ii) a prediction of the speed (e.g., in millimeters per second,        etc.) at which feedstock 411 will be deposited at each instant        during the printing of the article of manufacture, and    -   (iii) a prediction of the interval of time between when each        segment of feedstock 411 is irradiated and heated and when the        segment is deposited and tamped, and    -   (iv) a prediction of the interval of time between when each        portion of workpiece 406 is irradiated and heated and when        feedstock 411 is deposited and tamped onto that portion of        workpiece 406, and    -   (v) a location-specific thermal model of each portion on        workpiece 406 onto which feedstock 411 will be deposited and        tamped, which itself is based on, among other things, the        thermal model of the feedstock and the shape and mass of the        workpiece in the vicinity of each portion to be irradiated and        heated, which is derived from a model of the nascent article of        manufacture (i.e., workpiece) at each step of printing, which is        derived from the toolpath.

With regard to feedback, controller 409 takes as input:

-   -   (i) the thermal model of the feedstock, and    -   (ii) the location-specific thermal model of each portion on        workpiece 406 onto which feedstock 411 will be deposited and        tamped, and    -   (iii) periodic measurements of the temperature of the segment of        feedstock 411 that is within feedstock region 571-1, and    -   (iv) periodic measurements of the temperature of the segment of        feedstock 411 that is within feedstock region 571-2, and    -   (v) periodic measurements of the temperature of the segment of        feedstock 411 that is within feedstock region 571-3, and    -   (vi) periodic measurements of the temperature of that portion of        workpiece that is within workpiece region 572-1, and    -   (vii) periodic measurements of the temperature of that portion        of workpiece that is within workpiece region 572-2, and    -   (viii) periodic measurements of the temperature of that portion        of workpiece that is within workpiece region 572-3, and    -   (ix) the periodic measurements of the temperature of tamping        tool 408, and    -   (x) periodic measurements of the force of tamping tool 408 on        feedstock 411 at nip line segment 581.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use a thermal model of the        feedstock, a location-specific thermal model of each portion on        workpiece 406 onto which feedstock 411 will be deposited and        tamped, a prediction of whether the feedstock will be deposited        at a uniform or non-uniform rate, a prediction of the speed at        which the feedstock is deposited, and a prediction of the        interval between when each segment of feedstock and each portion        of the workpiece is irradiated and heated and when the segment        is deposited and tamped onto the portion of the workpiece.

FIG. 9 depicts a flowchart of the tasks performed by additivemanufacturing system 400. Because additive manufacturing system 400concurrently performs tasks on different segments of feedstock 411 anddifferent portions of workpiece 406, the tasks depicted in FIG. 9 areconcurrent.

At task 901:

-   -   (i) feedstock laser 441 generates laser beam 471 with an average        power during each time-interval, and    -   (ii) workpiece laser 442 generates laser beam 472 with an        average power during each time-interval, and        both as directed by controller 409. It will be clear to those        skilled in the art, after reading this disclosure, how to make        and use embodiments of the present invention that perform task        901.

At task 902, thermal sensor 771-1 periodically measures the temperatureof the segment of feedstock 411 that is within feedstock region 571-1and reports those measurements to controller 409. Additionally, thermalsensor 771-2 periodically measures the temperature of the segment offeedstock 411 that is within feedstock region 571-2 and reports thosemeasurements to controller 409. And furthermore, thermal sensor 771-3periodically measures the temperature of the segment of feedstock 411that is within feedstock region 571-3 and reports those measurements tocontroller 409. It will be clear to those skilled in the art, afterreading this disclosure, how to make and use embodiments of the presentinvention that perform task 901.

At task 903, thermal sensor 772-1 periodically measures the temperatureof that portion of workpiece 406 that is within workpiece region 572-1and reports those measurements to controller 409. Additionally, thermalsensor 772-2 periodically measures the temperature of that portion ofworkpiece 406 that is within workpiece region 572-2 and reports thosemeasurements to controller 409. And furthermore, thermal sensor 772-3periodically measures the temperature of that portion of workpiece 406that is within workpiece region 572-3 and reports those measurements tocontroller 409. It will be clear to those skilled in the art, afterreading this disclosure, how to make and use embodiments of the presentinvention that perform task 901.

At task 904, thermal sensor 773 periodically measures the temperature oftamping tool 408 and reports those measurements back to controller 409.Additionally, force gauge 413 periodically measures the force of tampingtool 408 on feedstock 411 at nip line segment 581 and reports thosemeasurements back to controller 409.

At task 905, optical instrument 461 irradiates and heats the segment offeedstock 411 that is within feedstock region 571-2 as directed bycontroller 409. It will be clear to those skilled in the art, afterreading this disclosure, how to make and use embodiments of the presentinvention that perform task 905.

At task 906, optical instrument 462 irradiates and heats the portion ofworkpiece 406 that is within workpiece region 572-2 as directed bycontroller 409. It will be clear to those skilled in the art, afterreading this disclosure, how to make and use embodiments of the presentinvention that perform task 906.

At task 907:

-   -   (i) optical instrument 461 adjusts a trait of laser beam 471        and/or the relationship of laser beam 471 to the segment of        feedstock 411 within feedstock region 571-2, and    -   (ii) optical instrument 462 adjusts a trait of laser beam 472        and/or the relationship of laser beam 472 to the portion of        workpiece 406 within workpiece region 572-2, and        both as directed by controller 409. Task 907 is described in        detail in FIG. 10 and in the accompanying text.

At task 908, additive manufacturing system 400 deposits a segment offeedstock 411 onto a portion of workpiece 406 and tamps the segment ontothe workpiece with tamping tool 408. It will be clear to those skilledin the art, after reading this disclosure, how to make and useembodiments of the present invention that perform task 908.

FIG. 10 depicts a flowchart of the details of task 907—adjusting opticalinstrument 461 and optical instrument 462, as directed by controller409. Controller 409 continually directs optical instrument 461 andoptical instrument 462 to make adjustments, and, therefore, the tasksdepicted in FIG. 10 are concurrent.

At task 1001, controller 409 directs optical instrument 461 toadjust—lengthen or shorten—the length of feedstock region 571-2 (i.e.,the length of feedstock 411 being irradiated by laser beam 471). Thisprovides controller 409 with a mechanism for adjusting the temperatureof each unit-length of feedstock 411 when it is deposited and tamped.For example—and assuming that everything else is constant—increasing thelength of feedstock region 571-2 spreads the heat energy of laser beam471 over a greater length of feedstock, which decreases the rate atwhich each unit-length of feedstock is heated. Conversely, decreasingthe length of feedstock region 571-2 concentrates the heat energy, whichincreases the rate at which each unit-length of feedstock is heated. Itwill be clear to those skilled in the art, after reading thisdisclosure, that being able to adjust the length of feedstock region571-2 is advantageous for, among other things, compensating forvariations in the rate at which feedstock 411 is deposited and tamped.

At task 1002, controller 409 directs optical instrument 461 toadjust—increase or decrease—the distance between pinch line segment 582and feedstock region 571-2. This provides controller 409 with amechanism for adjusting the temperature of each unit-length of feedstock411 when it is deposited and tamped. For example—and assuming everythingelse is constant—increasing the distance gives each unit-length offeedstock more time to cool before it is deposited and tamped.Conversely, decreasing the distance gives each unit segment of feedstockless time to cool before it is deposited and tamped. It will be clear tothose skilled in the art, after reading this disclosure, that being ableto adjust the distance between pinch line segment 582 and feedstockregion 571-2 is advantageous for, among other things, fine tuning thetemperature of each unit-length of feedstock 411 at the time that it isdeposited and tamped.

At task 1003, controller 409 directs optical instrument 461 to adjustthe irradiance of laser beam 471 on each unit-length of feedstock 411within feedstock region 571-2. This provides controller 409 with amechanism for adjusting the temperature of each unit-length of feedstock411 when it is deposited and tamped. For example—and assuming everythingelse is constant—increasing the irradiance on a unit-length of feedstock411 increases the rate at which it is heated. Conversely, decreasing theirradiance on a unit-length of feedstock 411 decreases the rate at whichit is heated. It will be clear to those skilled in the art, afterreading this disclosure, that being able to adjust the irradiance oflaser beam 471 on feedstock 411 is advantageous for, among other things,compensating for variations in the angle of incidence of laser beam 471on feedstock 411 caused by changes in the relative position of opticalinstrument 461 to feedstock 411. These changes are often caused bychanges in the contour of workpiece 406.

At task 1004, controller 409 directs optical instrument 461 to adjustthe angle of incidence of laser beam 471 on feedstock 411 withinfeedstock region 571-2. This provides controller 409 with anothermechanism for adjusting the temperature of each unit-length of feedstock411 when it is deposited and tamped. For example—and assuming everythingelse is constant—adjusting the angle of incidence of laser beam 471 onfeedstock 411 changes the effective irradiance on each unit-length offeedstock 411. It will be clear to those skilled in the art, afterreading this disclosure, that being able to adjust the angle ofincidence of laser beam 471 on feedstock 411 is advantageous for, amongother things, compensating for changes in the relative position ofoptical instrument 461 to feedstock 411. These changes are often causedby changes in the contour of workpiece 406.

At task 1005, controller 409 directs optical instrument 462 toadjust—lengthen or shorten—the length of workpiece region 572-2 (i.e.,the portion of workpiece 406 being irradiated by laser beam 472). Thisprovides controller 409 with a mechanism for adjusting the temperatureof each unit portion of workpiece 406 when it is deposited and tamped.For example—and assuming that everything else is constant—increasing thelength of workpiece region 572-2 spreads the heat energy of laser beam472 over a greater portion of workpiece 406, which decreases the rate atwhich each unit portion of workpiece 406 is heated. Conversely,decreasing the length of workpiece region 572-2 concentrates the heatenergy, which increases the rate at which each unit portion of workpiece406 is heated. It will be clear to those skilled in the art, afterreading this disclosure, that being able to adjust the length ofworkpiece region 572-2 is advantageous for, among other things,compensating for variations in the rate at which feedstock 411 isdeposited and tamped.

At task 1006, controller 409 directs optical instrument 462 toadjust—increase or decrease—the distance between pinch line 582 andworkpiece region 572-2. This provides controller 409 with a mechanismfor adjusting the temperature of each unit portion of workpiece 406 whenit is deposited and tamped. For example—and assuming everything else isconstant—increasing the distance gives each unit portion of workpiece406 more time to cool before it is deposited and tamped. Conversely,decreasing the distance gives each unit segment of feedstock less timeto cool before it is deposited and tamped. It will be clear to thoseskilled in the art, after reading this disclosure, that being able toadjust the distance between pinch line segment 582 and workpiece region572-2 is advantageous for, among other things, fine tuning thetemperature of each unit portion of workpiece 406 at the time that thecorresponding segment of feedstock 411 is deposited and tamped.

At task 1007, controller 409 directs optical instrument 462 to adjustthe irradiance of laser beam 472 on each unit portion of workpiece 406within workpiece region 572-2. This provides controller 409 with amechanism for adjusting the temperature of each unit portion ofworkpiece 406 at the time that the corresponding segment of feedstock411 is deposited and tamped. For example—and assuming everything else isconstant—increasing the irradiance on a unit portion of workpiece 406increases the rate at which it is heated. Conversely, decreasing theirradiance on a unit-area of workpiece 406 decreases the rate at whichit is heated. It will be clear to those skilled in the art, afterreading this disclosure, that being able to adjust the irradiance oflaser beam 472 on is advantageous for, among other things, compensatingfor variations in the angle of incidence of laser beam 472 on caused bychanges in the relative position of optical instrument 462 to. Thesechanges are often caused by changes in the contour of workpiece 406.

At task 1008, controller 409 directs optical instrument 462 to adjustthe angle of incidence of laser beam 472 on workpiece 406 withinworkpiece region 572-2. This provides controller 409 with anothermechanism for adjusting the temperature of each unit portion ofworkpiece 406 when it is deposited and tamped. For example—and assumingeverything else is constant—adjusting the angle of incidence of laserbeam 472 on workpiece 406 changes the effective irradiance on each unitportion of workpiece 406. It will be clear to those skilled in the art,after reading this disclosure, that being able to adjust the angle ofincidence of laser beam 472 on workpiece 406 is advantageous for, amongother things, compensating for changes in the relative position ofoptical instrument 462 to workpiece 406. These changes are often causedby changes in the contour of workpiece 406.

At task 1009, controller 409 directs optical instrument 462 to steerworkpiece laser beam 472 onto deposition path 591.

In accordance with the first illustrative embodiment, sensor array 415is not mechanically steered onto workpiece region 572-1, workpieceregion 572-2, or workpiece region 572-3. Instead, controller 409 picksthe temperature measurements for workpiece region 572-1, workpieceregion 572-2, or workpiece region 572-3 out of the thermal image fromsensor array 415 based on the location of deposition path 591 in thatimage. It will be clear to those skilled in the art, after reading thisdisclosure, how to accomplish this.

FIG. 11 depicts a flowchart of the relative timing of the tasksperformed on segment m of feedstock 411 and on portion n of workpiece406, wherein m and n are integers. In accordance with the firstillustrative embodiment segment m of feedstock 411 is deposited andtamped onto portion n of workpiece 406.

During time-interval Δt=m−3, the temperature of segment m of feedstock411 is measured by thermal sensor 771-1 and reported to controller 409.

During time-interval Δt=n−3, the temperature of portion n of workpiece406 is measured by thermal sensor 772-1 and reported to controller 409.

In accordance with the first illustrative embodiment, the duration oftime-interval Δt=m−3 equals the duration of time-interval Δt=n−3, andtime-interval Δt=m−3 is contemporaneous with time-interval Δt=n−3. Itwill be clear to those skilled in the art, however, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which the duration of time-interval Δt=m−3 does not equalthe duration of time-interval Δt=n−3. Furthermore, it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments of the present invention in whichtime-interval Δt=m−3 is not contemporaneous with time-interval Δt=n−3.And still furthermore, it will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=m−3overlaps, immediately precedes, immediately succeeds, precedes but notimmediately, or succeeds but not immediately time-interval Δt=n−3.

During time-interval Δt=m−2:

-   -   (i) controller 409 directs feedstock laser 441 to generate laser        beam 471 with a given average power, and    -   (ii) controller 409 directs optical instrument 461 to adjust a        trait of laser beam 471 and/or the relationship of laser beam        471 to feedstock 411, and    -   (iii) optical instrument 461 irradiates and heats segment m of        feedstock 411, and    -   (iv) the temperature of segment m of feedstock 411 is measured        by thermal sensor 771-2 and reported to controller 409.        In accordance with the first illustrative embodiment, the        duration of time-interval Δt=m−2 equals the duration of Δt=m−3.        It will be clear to those skilled in the art, however, after        reading this disclosure, how to make and use alternative        embodiments of the present invention in which the duration of        time-interval Δt=m−2 does not equal the duration of time        interval Δt=m−3. Furthermore, in accordance with the first        illustrative embodiment, time-interval Δt=m−2 is after, and is        mutually-exclusive of, time-interval Δt=m−3. It will be clear to        those skilled in the art, however, after reading this        disclosure, how to make and use alternative embodiments of the        present invention in which time-interval Δt=m−2 overlaps,        immediately succeeds, or succeeds but not immediately,        time-interval Δt=m−3.

During time-interval Δt=n−2:

-   -   (i) controller 409 directs workpiece laser 442 to generate laser        beam 472 with a given average power, and    -   (ii) controller 409 directs optical instrument 462 to adjust a        trait of laser beam 472 and/or the relationship of laser beam        472 to workpiece 406, and    -   (iii) controller 409 directs optical instrument 462 to steer        laser beam 472 onto deposition path 591, and    -   (iv) optical instrument 462 irradiates and heats portion n of        workpiece 406, and    -   (v) the temperature of portion n of workpiece 406 is measured by        thermal sensor 772-2 and reported to controller 409.

In accordance with the first illustrative embodiment, the duration oftime-interval Δt=n−2 equals the duration of Δt=n−3. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichthe duration of time-interval Δt=n−2 does not equal the duration of timeinterval Δt=n−3. Furthermore, in accordance with the first illustrativeembodiment, time-interval Δt=n−2 is after, and is mutually-exclusive of,time-interval Δt=n−3. It will be clear to those skilled in the art,however, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=n−2overlaps, immediately succeeds, or succeeds but not immediately,time-interval Δt=n−3.

In accordance with the first illustrative embodiment, the duration oftime-interval Δt=m−2 equals the duration of time-interval Δt=n−2, andtime-interval Δt=m−2 is contemporaneous with time-interval Δt=n−2. Itwill be clear to those skilled in the art, however, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which the duration of time-interval Δt=m−2 does not equalthe duration of time-interval Δt=n−2. Furthermore, it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments of the present invention in whichtime-interval Δt=m−2 is not contemporaneous with time-interval Δt=n−2.And still furthermore, it will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=m−2overlaps, immediately precedes, immediately succeeds, precedes but notimmediately, or succeeds but not immediately time-interval Δt=n−2.

During time-interval Δt=m−1, the temperature of segment m of feedstock411 is measured by thermal sensor 771-3 and reported to controller 409.

In accordance with the first illustrative embodiment, the duration oftime-interval Δt=m−1 equals the duration of Δt=m−2. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichthe duration of time-interval Δt=m−1 does not equal the duration of timeinterval Δt=m−2. Furthermore, in accordance with the first illustrativeembodiment, time-interval Δt=m−1 is after, and is mutually-exclusive of,time-interval Δt=m−2. It will be clear to those skilled in the art,however, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=m−1overlaps, immediately succeeds, or succeeds but not immediately,time-interval Δt=m−2.

During time-interval Δt=n−1, the temperature of portion n of workpiece406 is measured by thermal sensor 772-3 and reported to controller 409.

In accordance with the first illustrative embodiment, the duration oftime-interval Δt=n−1 equals the duration of Δt=n−2. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichthe duration of time-interval Δt=n−1 does not equal the duration of timeinterval Δt=n−2. Furthermore, in accordance with the first illustrativeembodiment, time-interval Δt=n−1 is after, and is mutually-exclusive of,time-interval Δt=n−2. It will be clear to those skilled in the art,however, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=n−1overlaps, immediately succeeds, or succeeds but not immediately,time-interval Δt=n−2.

In accordance with the first illustrative embodiment, the duration oftime-interval Δt=m−1 equals the duration of time-interval Δt=n−1, andtime-interval Δt=m−1 is contemporaneous with time-interval Δt=n−1. Itwill be clear to those skilled in the art, however, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which the duration of time-interval Δt=m−1 does not equalthe duration of time-interval Δt=n−1. Furthermore, it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments of the present invention in whichtime-interval Δt=m−1 is not contemporaneous with time-interval Δt=n−1.And still furthermore, it will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=m−1overlaps, immediately precedes, immediately succeeds, precedes but notimmediately, or succeeds but not immediately time-interval Δt=n−1.

During time-interval Δt=m=n, segment m of feedstock 411 is deposited andtamped onto portion n of workpiece 406.

In accordance with the first illustrative embodiment, the duration oftime-interval Δt=m equals the duration of Δt=m−1. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichthe duration of time-interval Δt=m does not equal the duration of timeinterval Δt=m−1. Furthermore, in accordance with the first illustrativeembodiment, time-interval Δt=m is after, and is mutually-exclusive of,time-interval Δt=m−1. It will be clear to those skilled in the art,however, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=moverlaps, immediately succeeds, or succeeds but not immediately,time-interval Δt=m−1.

In accordance with the first illustrative embodiment, the duration oftime-interval Δt=n equals the duration of Δt=n−1. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichthe duration of time-interval Δt=n does not equal the duration of timeinterval Δt=n−1. Furthermore, in accordance with the first illustrativeembodiment, time-interval Δt=n is after, and is mutually-exclusive of,time-interval Δt=n−1. It will be clear to those skilled in the art,however, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=noverlaps, immediately succeeds, or succeeds but not immediately,time-interval Δt=n−1.

In accordance with the first illustrative embodiment, feedstock laser441 and workpiece laser 442 are not mounted on deposition head 107because they are too heavy. It will be clear to those skilled in theart, after reading this disclosure, how to make and use alternativeembodiments of the present invention that use a plurality—perhaps tensor hundreds—of relatively-low-power lightweight lasers that are mountedon the deposition head to provide the laser beams to heat the feedstockand/or the workpiece. Furthermore, it will be clear to those skilled inthe art, after reading this disclosure, how to convey the laser beamsfrom their lasers to the deposition head via free-space optics (i.e.,without using an optical cable).

FIG. 12 depicts an illustration of additive manufacturing system 1200 inaccordance with the second illustrative embodiment of the presentinvention. Additive manufacturing system 1200 fabricates an article ofmanufacture by successively depositing segments of fiber-reinforcedthermoplastic feedstock (e.g., filament, tape, etc.) onto a workpieceuntil the article of manufacture is complete.

Additive manufacturing system 1200 is similar to additive manufacturingsystem 400 fabricates in that they both fabricate an article ofmanufacture by successively depositing segments of fiber-reinforcedthermoplastic feedstock (e.g., filament, tape, etc.) onto a workpieceuntil the article of manufacture is complete. In contrast, additivemanufacturing system 1200 is unlike additive manufacturing system 400 inthat system 1200 uses:

-   -   (i) a two-stage heating system that comprises two laser beams        and two optical instruments to irradiate and heat the feedstock,        and    -   (ii) a two-stage heating system that comprises two lasers beams        and two optical instruments to irradiate and heat the workpiece.        A two-stage heating system is advantageous over a single-stage        heating system in that it provides finer control of the        temperature of the feedstock and the workpiece and does so with        less-expensive lasers.

Additive manufacturing system 1200 comprises: platform 1201, robot mount1202, robot 1203, build plate support 1204, build plate 1205, workpiece1206, deposition head 1207, tamping tool 1208, controller 1209,feedstock reel 1210, feedstock 1211, accumulator 1212, sensor array1215, feedstock laser 1240, feedstock laser 1241, workpiece laser 1242,workpiece laser 1243, optical cable 1250, optical cable 1251, opticalcable 1252, optical cable 1253, sensor cable 1254, optical instrument1260, optical instrument 1261, optical instrument 1262, opticalinstrument 1263, laser beam 1270, laser beam 1271, laser beam 1272,laser beam 1273, feedstock laser control cable 1291, and workpiece lasercontrol cable 1292, interrelated as shown.

FIG. 13a depicts a close-up of workpiece 1206, deposition head 1207,tamping tool 1208, feedstock 1211, sensor array 1215, optical instrument1260, optical instrument 1261, optical instrument 1262, opticalinstrument 1263, optical cable 1250, optical cable 1251, optical cable1252, optical cable 1253, sensor cable 1254, laser beam 1270, laser beam1271, laser beam 1272, laser beam 1273, feedstock region 1371-1,feedstock region 1371-2, feedstock region 1371-3, workpiece region1372-1, workpiece region 1372-2, workpiece region 1372-3, nip linesegment 1381, and pinch line segment 1382, interrelated as shown.

FIG. 13b depicts a close-up of workpiece 1206, deposition head 1207,tamping tool 1208, feedstock 1211, feedstock region 1371-1, feedstockregion 1371-2, feedstock region 1371-3, workpiece region 1372-1,workpiece region 1372-2, workpiece region 1372-3, pinch line segment1382, and deposition path 1391 all as seen along cross-section CC-CC asdepicted in FIG. 13 a.

FIG. 14 depicts a close-up of workpiece 1206, deposition head 1207,tamping tool 1208, feedstock 1211, feedstock region 1371-1, feedstockregion 1371-2, feedstock region 1371-3, workpiece region 1372-1,workpiece region 1372-2, workpiece region 1372-3, pinch line segment1382, and deposition path 1391, all as seen along cross-section CC-CC asdepicted in FIG. 13 a.

FIG. 14 differs from FIG. 13a in that the curvature of deposition path1391 in FIG. 13a curves to the right (from the perspective of depositionhead 1207) whereas deposition path 1391 in FIG. 14 curves to the left.This is because additive manufacturing system 1200 steers laser beam1272, workpiece region 1372-1, workpiece region 1372-2, and workpieceregion 1372-3 onto deposition path 1391 as deposition path 1391 meanderson workpiece 1206.

Although the second illustrative embodiment comprises a total of fourlasers, it will be clear to those skilled in the art, after reading thisdisclosure, how to make and use embodiments of the present inventionthat use any number of lasers (e.g., three lasers, five lasers, sixlasers, seven lasers, eight lasers, ten lasers, twenty lasers,one-hundred lasers, etc.).

Although the second illustrative embodiment apportions its four lasersevenly between the feedstock and the workpiece, it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments of the present invention that apportion itslasers to the feedstock and workpiece in any combination (e.g., onelaser dedicated to the feedstock and three lasers dedicated to theworkpiece, three lasers dedicated to the feedstock and one laserdedicated to the workpiece, etc.).

Although the second illustrative embodiment dedicates two lasers toheating the feedstock and two lasers to heating the workpiece, it willbe clear to those skilled in the art, after reading this disclosure, howto make and use alternative embodiments of the present invention that donot dedicate each laser to either the feedstock of the workpiece. As aconsequence, it will be clear to those skilled in the art, after readingthis disclosure, how to make and use alternative embodiments of thepresent invention in which one or more lasers switch, as needed, betweenheating the feedstock and heating the laser. For example, one laser isdedicated to heating the feedstock, a second laser is dedicated toheating the workpiece, and a third laser heats whichever—the feedstockor the workpiece—needs heating at any given moment.

Platform 1201 is identical to platform 401 in the first illustrativeembodiment and performs the same function in exactly the same way. Itwill be clear to those skilled in the art how to make and use platform1201.

Robot mount 1202 is identical to robot mount 402 in the firstillustrative embodiment and performs exactly the same function inexactly the same way. It will be clear to those skilled in the art howto make and use robot mount 1202.

Robot 1203 is identical to robot 103 in the first illustrativeembodiment and performs exactly the same function in exactly the sameway. It will be clear to those skilled in the art how to make and userobot 1203.

Build plate support 1204 is identical to build plate support 404 in thefirst illustrative embodiment and performs exactly the same function inexactly the same way. It will be clear to those skilled in the art howto make and use build plate support 1204.

Build plate 1205 is identical to build plate 405 in the firstillustrative embodiment and performs exactly the same function inexactly the same way. It will be clear to those skilled in the art howto make and use build plate 1205.

Workpiece 1206 is identical to workpiece 406 in the first illustrativeembodiment and performs exactly the same function in exactly the sameway.

Deposition head 1207 is the end effector of robot 1203 and comprises:

-   -   (i) a feedstock guide that is identical to the feedstock guide        in the first illustrative embodiment and performs exactly the        same function in exactly the same way. It will be clear to those        skilled in the art how to make and use the feedstock guide.    -   (ii) tamping tool 1208, which first pinches and then tamps each        segment of feedstock 1211 onto the corresponding portion of        workpiece 1206.    -   (iii) a feedstock cutter—under the direction of controller        1209—is identical to feedstock cutter in the first illustrative        embodiment and performs exactly the same function in exactly the        same way. It will be clear to those skilled in the art how to        make and use the feedstock cutter.    -   (iv) optical instrument 1260, which takes laser beam 1270 from        optical cable 1250, and—under the direction of controller        1209—conditions laser beam 1270 and directs it onto feedstock        region 1371-2.    -   (v) optical instrument 1261, which takes laser beam 1271 from        optical cable 1251, and—under the direction of controller        1209—conditions laser beam 1271 and directs it onto feedstock        region 1371-1.    -   (vi) optical instrument 1262, which takes laser beam 1272 from        optical cable 1252, and—under the direction of controller        1209—conditions laser beam 1272 and directs it onto workpiece        region 1372-2.    -   (vii) optical instrument 1263, which takes laser beam 1273 from        optical cable 1253, and—under the direction of controller        1209—conditions laser beam 1273 and directs it onto workpiece        region 1372-3.    -   (viii) sensor array 1215, which measures the temperature of        feedstock region 1371-2, workpiece region 1372-2, and tamping        tool 1208 and reports those measurements to controller 1209 via        sensor cable 1254    -   (ix) force gauge 1213 that continually measures the force of        tamping tool 1208 on feedstock 1211 at nip line segment 1381 and        reports those measurements back to controller 1209 via sensor        cable 1254.    -   (x) structural support, which is similar to the structural        support in the first illustrative embodiment except that is also        supports optical instrument 1260 and optical instrument 1263 in        addition to optical instrument 1261, optical instrument 1262,        and sensor array 1215. Otherwise, the structural support        performs exactly the same function in exactly the same way. It        will be clear to those skilled in the art, after reading this        disclosure, how to make and use the structural support.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use deposition head 1207.

Tamping tool 1208 is identical to tamping tool 1208 in the firstillustrative embodiment and performs exactly the same function inexactly the same way. It will be clear to those skilled in the art howto make and use tamping tool 1208.

Controller 1209 comprises the hardware and software necessary to controlall aspects of fabricating the article of manufacture, including, butnot limited to:

-   -   (i) robot 1203 (which includes the location and motion of        deposition head 1207 and tamping tool 1208), and    -   (ii) build plate support 1204, and    -   (iii) the feedstock cutter, and    -   (iv) feedstock laser 1240, and    -   (v) feedstock laser 1241, and    -   (vi) workpiece laser 1242, and    -   (vii) workpiece laser 1243, and    -   (viii) optical instrument 1260, and    -   (ix) optical instrument 1261, and    -   (x) optical instrument 1262, and    -   (xi) optical instrument 1263, and    -   (xii) accumulator 1212.        To accomplish this controller 1209 relies on a combination of        feedforward and feedback, as described in detail below and in        the accompanying drawings. It will be clear to those skilled in        the art, after reading this disclosure, how to make and use        controller 1209.

Feedstock reel 1210 is identical to feedstock reel 410 in the firstillustrative embodiment and performs exactly the same function inexactly the same way. It will be clear to those skilled in the art howto make and use feedstock reel 1210.

Feedstock 1211 is identical to feedstock 411 in the first illustrativeembodiment and performs exactly same function in exactly the same way.It will be clear to those skilled in the art how to make and usefeedstock 1211.

Accumulator 1212 is identical to accumulator 412 in the firstillustrative embodiment and performs exactly the same function inexactly the same way. It will be clear to those skilled in the art howto make and use accumulator 1212.

Force Gauge 1213—is a mechanical strain gauge that continually measuresthe force of tamping tool 1208 on feedstock 1211 at nip line segment1381 and reports those measurements back to controller 1209 via sensorcable 1254. It will be clear to those skilled in the art how to make anduse force gauge 1213.

Sensor array 1215 is identical to sensor array 415 in the firstillustrative embodiment and performs exactly the same function inexactly the same way. It will be clear to those skilled in the art howto make and use sensor array 1215.

Feedstock laser 1240 is a variable-power laser that generates laser beam1270 and conveys it to optical instrument 1260 via optical cable 1250.In accordance with the second illustrative embodiment, feedstock laser1240 is directed by controller 1209 to generate laser beam 1270 with aspecific average power over a given time-interval. In accordance withthe second illustrative embodiment, laser beam 1270 is characterized bya wavelength λ=980 nm and has a maximum power output of 200 Watts.

In accordance with the illustrative embodiment, feedstock laser 1240 isa continuous-wave laser. It will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention that use a pulsed laser. In anycase, it will be clear to those skilled in the art how to make and usefeedstock laser 1240.

Feedstock laser 1241 is a variable-power laser that generates laser beam1271 and conveys it to optical instrument 1261 via optical cable 1251.In accordance with the second illustrative embodiment, feedstock laser1241 is directed by controller 1209 to generate laser beam 1271 with aspecific average power over a given time-interval. In accordance withthe second illustrative embodiment, laser beam 1271 is characterized bya wavelength λ=980 nm and has a maximum power output of 200 Watts.

In accordance with the illustrative embodiment, feedstock laser 1241 isa continuous-wave laser. It will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention that use a pulsed laser. In anycase, it will be clear to those skilled in the art how to make and usefeedstock laser 1241.

Workpiece laser 1242 is a variable-power laser that generates laser beam1272 and conveys it to optical instrument 1262 via optical cable 1252.In accordance with the second illustrative embodiment, workpiece laser1242 is directed by controller 1209 to generate laser beam 1272 with aspecific average power over a given time-interval. In accordance withthe second illustrative embodiment, laser beam 1272 is characterized bya wavelength λ=980 nm and has a maximum power output of 200 Watts.

In accordance with the illustrative embodiment, workpiece laser 1242 isa continuous-wave laser. It will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention that use a pulsed laser. In anycase, it will be clear to those skilled in the art how to make and useworkpiece laser 1242.

Workpiece laser 1243 is a variable-power laser that generates laser beam1273 and conveys it to optical instrument 1263 via optical cable 1253.In accordance with the second illustrative embodiment, workpiece laser1243 is directed by controller 1209 to generate laser beam 1273 with aspecific average power over a given time-interval. In accordance withthe second illustrative embodiment, laser beam 1273 is characterized bya wavelength λ=980 nm and has a maximum power output of 200 Watts.

In accordance with the illustrative embodiment, workpiece laser 1243 isa continuous-wave laser. It will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention that use a pulsed laser. In anycase, it will be clear to those skilled in the art how to make and useworkpiece laser 1243.

In accordance with the second illustrative embodiment, feedstock laser1240, feedstock laser 1241, workpiece laser 1242, and workpiece laser1243 are identical and generate laser beams characterized by the samewavelength. It will be clear to those skilled in the art, however, afterreading this disclosure, how to make and use alternative embodiments ofthe present invention in which one or more of the lasers:

(i) are not identical, or

(i) generate laser beams characterized by different wavelengths, or

(iii) have different maximum power output, or

(iv) any combination of i, ii, and iii.

Optical cable 1250 is identical to optical cable 451 in the firstillustrative embodiment. It will be clear to those skilled in the arthow to make and use optical cable 1250.

Optical cable 1251 is identical to optical cable 451 in the firstillustrative embodiment. It will be clear to those skilled in the arthow to make and use optical cable 1251.

Optical cable 1252 is identical to optical cable 451 in the firstillustrative embodiment. It will be clear to those skilled in the arthow to make and use optical cable 1252.

Optical cable 1253 is identical to optical cable 451 in the firstillustrative embodiment. It will be clear to those skilled in the arthow to make and use optical cable 1253.

Sensor cable 1254 is identical to sensor cable 454 in the firstillustrative embodiment. It will be clear to those skilled in the arthow to make and use sensor cable 1254.

Optical instrument 1260 is identical to optical instrument 461 in thefirst illustrative embodiment and performs a similar function on thesegment of feedstock 1211 in feedstock region 1371-3. In particular,optical instrument 1260 is an optomechanical machine that comprisesoptics and actuators that receive laser beam 1270 from feedstock laser1240, via optical cable 1250, conditions it under the direction ofcontroller 1209, and directs it onto the segment of feedstock 1211 thatis within feedstock region 1371-3. In accordance with the secondillustrative embodiment, optical instrument 1261 comprises:

-   -   (i) an actuator and an optic that, under the direction of        controller 1209, adjusts the length of the segment of feedstock        1211 that is irradiated and heated by laser beam 1270 (i.e.,        adjusts the length of feedstock region 1371-3), and    -   (ii) an actuator and an optic that, under the direction of        controller 1209, adjusts the distance between pinch line segment        1382 and laser beam 1270 (i.e., adjusts the distance between        pinch line segment 1382 and feedstock region 1371-3), and    -   (iii) an actuator and an optic that, under the direction of        controller 1209, adjusts the irradiance within each unit-area of        laser beam 1270 on feedstock 1211, and    -   (iv) an actuator and an optic that, under the direction of        controller 1209, adjusts the angle of incidence of laser beam        1270 on feedstock 1211.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use optical instrument 1260.

Optical instrument 1261 is identical to optical instrument 461 in thefirst illustrative embodiment and performs exactly the same function inexactly the same way. In particular, optical instrument 1261 is anoptomechanical machine that comprises optics and actuators that receivelaser beam 1271 from feedstock laser 1241, via optical cable 1251,conditions it under the direction of controller 1209, and directs itonto the segment of feedstock 1211 that is within feedstock region1371-2. In accordance with the second illustrative embodiment, opticalinstrument 1261 comprises:

-   -   (i) an actuator and an optic that, under the direction of        controller 1209, adjusts the length of the segment of feedstock        1211 that is irradiated and heated by laser beam 1271 (i.e.,        adjusts the length of feedstock region 1371-2), and    -   (ii) an actuator and an optic that, under the direction of        controller 1209, adjusts the distance between pinch line segment        1382 and laser beam 1271 (i.e., adjusts the distance between        pinch line segment 1382 and feedstock region 1371-2), and    -   (iii) an actuator and an optic that, under the direction of        controller 1209, adjusts the irradiance within each unit-area of        laser beam 1271 on feedstock 1211, and    -   (iv) an actuator and an optic that, under the direction of        controller 1209, adjusts the angle of incidence of laser beam        1271 on feedstock 1211.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use optical instrument 1261.

Optical instrument 1262 is identical to optical instrument 462 in thefirst illustrative embodiment and performs exactly the same function inexactly the same way. In particular, optical instrument 1262 is anoptomechanical machine that comprises optics and actuators that receivelaser beam 1272 from workpiece laser 1242, via optical cable 1252,conditions it, and directs it onto the portion of workpiece 1206 that iswithin workpiece region 1372-2 under the direction of controller 1209.In accordance with the second illustrative embodiment, opticalinstrument 1261 comprises:

-   -   (i) an actuator and an optic that, under the direction of        controller 1209, adjusts the length of the portion of workpiece        1206 that is irradiated and heated by laser beam 1272 (i.e.,        adjusts the length of workpiece region 1372-2), and    -   (ii) an actuator and an optic that, under the direction of        controller 1209, adjusts the distance between pinch line segment        1382 and laser beam 1272 (i.e., adjusts the distance between        pinch line segment 1382 and workpiece region 1372-2), and    -   (iii) an actuator and an optic that, under the direction of        controller 1209, adjusts the irradiance within each unit-area of        laser beam 1272 on workpiece 1206, and    -   (iv) an actuator and an optic that, under the direction of        controller 1209, adjusts the angle of incidence of laser beam        1272 on workpiece 1206, and    -   (v) an actuator that steers laser beam 1272 onto deposition path        1391.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use optical instrument 1262.

Optical instrument 1263 is identical to optical instrument 462 in thefirst illustrative embodiment and performs a similar function on theportion of workpiece 1206 in workpiece region 1372-3. In particular,optical instrument 1263 is an optomechanical machine that comprisesoptics and actuators that receive laser beam 1273 from workpiece laser1243, via optical cable 1253, conditions it, and directs it onto theportion of workpiece 1206 that is within workpiece region 1372-3 underthe direction of controller 1209. In accordance with the secondillustrative embodiment, optical instrument 1263 comprises:

-   -   (i) an actuator and an optic that, under the direction of        controller 1209, adjusts the length of the portion of workpiece        1206 that is irradiated and heated by laser beam 1273 (i.e.,        adjusts the length of workpiece region 1372-3), and    -   (ii) an actuator and an optic that, under the direction of        controller 1209, adjusts the distance between pinch line segment        1382 and laser beam 1273 (i.e., adjusts the distance between        pinch line segment 1382 and workpiece region 1372-3), and    -   (iii) an actuator and an optic that, under the direction of        controller 1209, adjusts the irradiance within each unit-area of        laser beam 1273 on workpiece 1206, and    -   (iv) an actuator and an optic that, under the direction of        controller 1209, adjusts the angle of incidence of laser beam        1273 on workpiece 1206, and    -   (v) an actuator that steers laser beam 1273 onto deposition path        1391.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use optical instrument 1263.

Feedstock laser control cable 1290 is an electrical cable, in well-knownfashion, that carries instructions from controller 1209 to feedstocklaser 1240, which instructions control all aspects (e.g., power, etc.)of feedstock laser 1240. It will be clear to those skilled in the arthow to make and use feedstock laser control cable 1290.

Feedstock laser control cable 1291 is an electrical cable, in well-knownfashion, that carries instructions from controller 1209 to feedstocklaser 1241, which instructions control all aspects (e.g., power, etc.)of feedstock laser 1241. It will be clear to those skilled in the arthow to make and use feedstock laser control cable 1291.

Workpiece laser control cable 1292 is an electrical cable, in well-knownfashion, that carries instructions from controller 1209 to workpiecelaser 1242, which instructions control all aspects (e.g., power, etc.)of workpiece laser 1242. It will be clear to those skilled in the arthow to make and use feedstock laser control cable 1292.

Workpiece laser control cable 1293 is an electrical cable, in well-knownfashion, that carries instructions from controller 1209 to workpiecelaser 1243, which instructions control all aspects (e.g., power, etc.)of workpiece laser 1243. It will be clear to those skilled in the arthow to make and use feedstock laser control cable 1293.

Feedstock region 1371-1, feedstock region 1371-2, and feedstock region1371-3 are three volumes in space through which feedstock 1211 passes.

The length of feedstock region 1371-1 is defined as the length offeedstock 1211 within feedstock region 1371-1. In accordance with thesecond illustrative embodiment, the length of feedstock region 1371-1 is15 mm, but it will be clear to those skilled in the art, after readingthis disclosure, how to make and use alternative embodiments in whichthe length of feedstock region 1371-1 is different.

The length of feedstock region 1371-2 is defined as the length offeedstock 1211 being irradiated by laser beam 1271. In accordance withthe second illustrative embodiment, the length of feedstock region1371-2 is continually adjusted by optical instrument 1261 under thedirection of controller 1209. In accordance with the second illustrativeembodiment, the minimum length of feedstock region 1371-2 is 5 mm andthe maximum length is 15 mm, but it will be clear to those skilled inthe art, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which the minimum and maximumlengths are different.

The length of feedstock region 1371-3 is defined as the length offeedstock 1211 within feedstock region 1371-3. In accordance with thesecond illustrative embodiment, the length of feedstock region 1371-3 is10 mm, but it will be clear to those skilled in the art, after readingthis disclosure, how to make and use alternative embodiments in whichthe length of the feedstock region 1373-3 is different.

In accordance with the second illustrative embodiment, the distance offeedstock region 1371-1 from pinch line segment 1382 (as measured alongthe length of feedstock 1211) is 55 mm, but it will be clear to thoseskilled in the art, after reading this disclosure, how to make and usealternative embodiments in which the distance is different.

In accordance with the second illustrative embodiment, the distance offeedstock region 1371-2 from pinch line segment 1382 (as measured alongthe length of feedstock 1211) is continually adjusted by opticalinstrument 1261 under the direction of controller 1209. In accordancewith the second illustrative embodiment, the minimum distance offeedstock region 1371-2 from pinch line segment 1382 is 25 mm and themaximum distance is 35 mm, but it will be clear to those skilled in theart, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which the minimum and maximumlengths are different.

In accordance with the second illustrative embodiment, the distance offeedstock region 1371-3 from pinch line segment 1382 (as measured alongthe length of feedstock 1211) is 5 mm but it will be clear to thoseskilled in the art, after reading this disclosure, how to make and usealternative embodiments in which the distance is different.

Workpiece region 1372-1, workpiece region 1372-2, and workpiece region1372-3 are three volumes in space through which deposition path 1391passes.

The length of workpiece region 1372-1 is defined as the length ofdeposition path 1391 within workpiece region 1372-1. In accordance withthe second illustrative embodiment, the length of workpiece region1372-1 is 15 mm, but it will be clear to those skilled in the art, afterreading this disclosure, how to make and use alternative embodiments inwhich the length of workpiece region 1372-1 is different.

The length of workpiece region 1372-2 is defined as the length ofdeposition path 1391 being irradiated by laser beam 1271. In accordancewith the second illustrative embodiment, the length of feedstock region1372-2 is continually adjusted by optical instrument 1262 under thedirection of controller 1209. In accordance with the second illustrativeembodiment, the minimum length of workpiece region 1372-2 is 5 mm andthe maximum length is 15 mm, but it will be clear to those skilled inthe art, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which the minimum and maximumlengths are different.

The length of workpiece region 1372-3 is defined as the length ofdeposition path 1391 within workpiece region 1372-3. In accordance withthe second illustrative embodiment, the length of workpiece region1372-3 is 10 mm, but it will be clear to those skilled in the art, afterreading this disclosure, how to make and use alternative embodiments inwhich the length of the workpiece region 1373-3 is different.

In accordance with the second illustrative embodiment, the distance ofworkpiece region 1372-1 from pinch line segment 1382 (as measured alongthe length of deposition path 1391) is 55 mm, but it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments in which the distance is different.

In accordance with the second illustrative embodiment, the distance ofworkpiece region 1372-2 from pinch line segment 1382 (as measured alongthe length of deposition path 1391) is continually adjusted by opticalinstrument 1262 under the direction of controller 1209. In accordancewith the second illustrative embodiment, the minimum distance ofworkpiece region 1372-2 from pinch line segment 1382 is 25 mm and themaximum distance is 35 mm, but it will be clear to those skilled in theart, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which the minimum and maximumlengths are different.

Nip line segment 1381 is the line segment on the circumferential surfaceof tamping tool 1208 where tamping tool 1208 exerts the maximum radialforce on feedstock 1211.

Pinch line segment 1382 is the line segment on the circumferentialsurface of tamping tool 1208 where tamping tool 1208 first pinches aunit-length of feedstock 1211 between tamping tool 1208 and workpiece1206 so that any movement of feedstock 1211 parallel to the rotationalaxis of tamping tool 1208 is substantially constrained.

Deposition path 1391 is a line on the surface of workpiece 1206 wherefeedstock 1211 is to be deposited and tamped. In FIG. 13b , depositionpath 1391 curves to the left. In contrast, in FIG. 14, deposition path1391 curves to the right.

FIG. 15 depicts a schematic diagram of the heating and sensorarchitecture for additive manufacturing system 1200, which irradiatesand heats feedstock 1211 and workpiece 1206 and measures the temperatureof feedstock 1211, workpiece 1206, and tamping tool 1208.

As shown in FIG. 15:

-   -   (i) feedstock laser 1240 provides laser beam 1270 to optical        instrument 1260 via optical cable 1250, and    -   (ii) feedstock laser 1241 provides laser beam 1271 to optical        instrument 1261 via optical cable 1251, and    -   (iii) workpiece laser 1242 provides laser beam 1272 to optical        instrument 1262 via optical cable 1252, and    -   (iii) workpiece laser 1243 provides laser beam 1273 to optical        instrument 1263 via optical cable 1253.

Under the direction of controller 1209:

-   -   (i) optical instrument 1260 irradiates and heats the segment of        feedstock that is within feedstock region 1371-3, and    -   (ii) optical instrument 1261 irradiates and heats the segment of        feedstock that is within feedstock region 1371-2, and    -   (iii) optical instrument 1262 irradiates and heats the portion        of workpiece 1206 that is within workpiece region 1372-2, and    -   (iv) optical instrument 1263 irradiates and heats the portion of        workpiece 1206 that is within workpiece region 1372-3.

Thermal sensor 1571-1 periodically measures the temperature of thesegment of feedstock that is within feedstock region 1371-1 and reportsthose measurements back to controller 1209. Thermal sensor 1571-2periodically measures the temperature of the segment of feedstock thatis within feedstock region 1371-2 and reports those measurements back tocontroller 1209. Thermal sensor 1571-3 periodically measures thetemperature of the segment of feedstock that is within feedstock region1371-3 and reports those measurements back to controller 1209.

Thermal sensor 1572-1 periodically measures the temperature of thatportion of workpiece 1206 that is within workpiece region 1372-1 andreports those measurements back to controller 1209. Thermal sensor1572-2 periodically measures the temperature of that portion ofworkpiece 1206 that is within workpiece region 1372-2 and reports thosemeasurements back to controller 1209. Thermal sensor 1572-3 periodicallymeasures the temperature of that portion of workpiece 1206 that iswithin workpiece region 1372-3 and reports those measurements back tocontroller 1209.

Thermal sensor 773 periodically measures the temperature of tamping tool1208 and reports those measurements back to controller 1209.

In accordance with the second illustrative embodiment, the temperaturemeasurements are made periodically at sixty (60) times per second, butit will be clear to those skilled in the art, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention that make periodic measurements at a different rate or thatmake measurements aperiodically or sporadically.

FIG. 16 depicts a schematic diagram of the sensor and controlarchitecture for that portion of additive manufacturing system 1200 thatirradiates and heats feedstock 1211 and workpiece 1206.

In accordance with the second illustrative embodiment, controller 1209uses a combination of feedforward and feedback to continually direct:

-   -   (i) feedstock laser 1240 to adjust the average power of laser        beam 1270 on the segment of feedstock that is within feedstock        region 1371-3, and    -   (ii) optical instrument 1260 to adjust the length of feedstock        region 1371-3, and    -   (iii) optical instrument 1260 to adjust the distance between        pinch line segment 1382 and feedstock region 1371-3, and    -   (iv) optical instrument 1260 to adjust the irradiance of laser        beam 1270 on the segment of feedstock 1211 within feedstock        region 1371-3, and    -   (v) optical instrument 1260 to adjust the angle of incidence of        laser beam 1270 on the segment of feedstock 1211 within        feedstock region 1371-3, and    -   (vi) feedstock laser 1241 to adjust the average power of laser        beam 1271 on the segment of feedstock that is within feedstock        region 1371-2, and    -   (vii) optical instrument 1261 to adjust the length of feedstock        region 1371-2, and    -   (viii) optical instrument 1261 to adjust the distance between        pinch line segment 1382 and feedstock region 1371-2, and    -   (ix) optical instrument 1261 to adjust the irradiance of laser        beam 1271 on the segment of feedstock 1211 within feedstock        region 1371-2, and    -   (x) optical instrument 1261 to adjust the angle of incidence of        laser beam 1271 on the segment of feedstock 1211 within        feedstock region 1371-2, and    -   (xi) workpiece laser 1242 to adjust the average power of laser        beam 1272 on the portion of workpiece that is within workpiece        region 1372-2, and    -   (xii) optical instrument 1262 to adjust the length of workpiece        region 1372-2, and    -   (xiii) optical instrument 1262 to adjust the distance between        pinch line segment 1382 and workpiece region 1372-2, and    -   (xiv) optical instrument 1262 to adjust the irradiance of laser        beam 1272 on the portion of workpiece 1206 within workpiece        region 1372-2, and    -   (xv) optical instrument 1262 to adjust the angle of incidence of        laser beam 1272 on the portion of workpiece 1206 within        workpiece region 1372-2, and    -   (xvi) optical instrument 1262 to steer laser beam 1272 onto        deposition path, and    -   (xvii) workpiece laser 1243 to adjust the average power of laser        beam 1273 on the portion of workpiece that is within workpiece        region 1372-3, and    -   (xviii) optical instrument 1263 to adjust the length of        workpiece region 1372-3, and    -   (xix) optical instrument 1263 to adjust the distance between        pinch line segment 1383 and workpiece region 1372-3, and    -   (xx) optical instrument 1263 to adjust the irradiance of laser        beam 1273 on the portion of workpiece 1206 within workpiece        region 1372-3, and    -   (xxi) optical instrument 1263 to adjust the angle of incidence        of laser beam 1273 on the portion of workpiece 1206 within        workpiece region 1372-3, and    -   (xxii) optical instrument 1263 to steer laser beam 1273 onto        deposition path 1391, and    -   (xxiii) accumulator 1212 to feed feedstock 1211 to deposition        head 1207, and    -   (xxiv) robot 1203 to advance tamping tool 1208 to deposit and        tamp feedstock 1211 onto workpiece 1206, and        based on:    -   (i) knowledge of the toolpath (e.g., G-code, etc.) for the        article of manufacture to be printed (and the geometry of the        workpiece at each time-interval, which can be derived from that        toolpath), and    -   (ii) a thermal model of the feedstock 1211, and    -   (iii) a location-specific thermal model of each portion on        workpiece 1206 onto which feedstock 1211 will be deposited and        tamped (which can be derived from the thermal model of the        feedstock 1211 and the geometry of the workpiece at each instant        during fabrication), and    -   (iv) periodic measurements of the temperature of the segment of        feedstock 1211 that is within feedstock region 1371-1, and    -   (v) periodic measurements of the temperature of the segment of        feedstock 1211 that is within feedstock region 1371-2, and    -   (vi) periodic measurements of the temperature of the segment of        feedstock 1211 that is within feedstock region 1371-3, and    -   (vii) periodic measurements of the temperature of that portion        of workpiece that is within workpiece region 1372-1, and    -   (viii) periodic measurements of the temperature of that portion        of workpiece that is within workpiece region 1372-2, and    -   (ix) periodic measurements of the temperature of that portion of        workpiece that is within workpiece region 1372-3, and    -   (x) periodic measurements of the temperature of tamping tool        1208, and    -   (xi) periodic measurements of the force of tamping tool 1208 on        feedstock 1211 at nip line segment 1381.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use embodiments of the present        invention that accomplish this, whether with traditional        imperative programming or with an artificial neural network.

With regard to feedforward, controller 1209 takes as input:

-   -   (i) the toolpath (e.g., G-code, etc.) for the article of        manufacture to be printed, in well-known fashion, and    -   (ii) a thermal model of the feedstock, which itself is based on,        among other things, the thermal properties of the resin, the        mass of resin per unit-length of feedstock, the profile of the        feedstock (e.g., filament, tape, circular, rectangular, etc.),        the thermal properties of the reinforcing fibers, the number of        fibers per unit-length of feedstock, the mass of the fibers per        unit-length of feedstock, and the length and orientation of the        fibers in the feedstock (e.g., continuous, chopped, medium, ball        milled, etc.),        and generates therefrom:    -   (i) a prediction of whether feedstock 1211 will be deposited at        a uniform or non-uniform rate at each instant during the        printing of the article of manufacture (because, for example and        without limitation, the deposition starts and stops,        accelerates, decelerates and occurs uniformly because of turns,        contours, cuts, etc.), and    -   (ii) a prediction of the speed (e.g., in millimeters per second,        etc.) at which feedstock 1211 will be deposited at each instant        during the printing of the article of manufacture, and    -   (iii) a prediction of the interval of time between when each        segment of feedstock 1211 is irradiated and heated and when the        segment is deposited and tamped, and    -   (iv) a prediction of the interval of time between when each        portion of workpiece 1206 is irradiated and heated and when        feedstock 1211 is deposited and tamped onto that portion of        workpiece 1206, and    -   (v) a location-specific thermal model of each portion on        workpiece 1206 onto which feedstock 1211 will be deposited and        tamped, which itself is based on, among other things, the        thermal model of the feedstock and the shape and mass of the        workpiece in the vicinity of each portion to be irradiated and        heated, which is derived from a model of the nascent article of        manufacture (i.e., workpiece) at each step of printing, which is        derived from the toolpath.

With regard to feedback, controller 1209 takes as input:

-   -   (i) the thermal model of the feedstock, and    -   (ii) the location-specific thermal model of each portion on        workpiece 1206 onto which feedstock 1211 will be deposited and        tamped, and    -   (iii) periodic measurements of the temperature of the segment of        feedstock 1211 that is within feedstock region 1371-1, and    -   (iv) periodic measurements of the temperature of the segment of        feedstock 1211 that is within feedstock region 1371-2, and    -   (v) periodic measurements of the temperature of the segment of        feedstock 1211 that is within feedstock region 1371-3, and    -   (vi) periodic measurements of the temperature of that portion of        workpiece that is within workpiece region 1372-1, and    -   (vii) periodic measurements of the temperature of that portion        of workpiece that is within workpiece region 1372-2, and    -   (viii) periodic measurements of the temperature of that portion        of workpiece that is within workpiece region 1372-3, and    -   (ix) periodic measurements of the temperature of tamping tool        1208, and    -   (x) periodic measurements of the force of tamping tool 1208 on        feedstock 1211 at nip line segment 1381.        It will be clear to those skilled in the art, after reading this        disclosure, how to make and use a thermal model of the        feedstock, a location-specific thermal model of each portion on        workpiece 1206 onto which feedstock 1211 will be deposited and        tamped, a prediction of whether the feedstock will be deposited        at a uniform or non-uniform rate, a prediction of the speed at        which the feedstock is deposited, and a prediction of the        interval between when each segment of feedstock and each portion        of workpiece is irradiated and heated and when the segment of        feedstock is deposited and tamped onto the portion of the        workpiece.

FIG. 17 depicts a flowchart of the tasks performed by additivemanufacturing system 1200. Because additive manufacturing system 1200concurrently performs tasks on different segments of feedstock 1211 anddifferent portions of workpiece 1206, the tasks depicted in FIG. 17 areconcurrent.

At task 1701:

-   -   (i) feedstock laser 1240 generates laser beam 1270 with an        average power during each time-interval, and    -   (ii) feedstock laser 1241 generates laser beam 1271 with an        average power during each time-interval, and    -   (iii) workpiece laser 1242 generates laser beam 1272 with an        average power during each time-interval, and    -   (iv) workpiece laser 1243 generates laser beam 1273 with an        average power during each time-interval,        all as directed by controller 1209. It will be clear to those        skilled in the art, after reading this disclosure, how to make        and use embodiments of the present invention that perform task        1701.

At task 1702, thermal sensor 1571-1 periodically measures thetemperature of the segment of feedstock 1211 that is within feedstockregion 1371-1 and reports those measurements to controller 1209.Additionally, thermal sensor 1571-2 periodically measures thetemperature of the segment of feedstock 1211 that is within feedstockregion 1371-2 and reports those measurements to controller 1209. Andfurthermore, thermal sensor 1571-3 periodically measures the temperatureof the segment of feedstock 1211 that is within feedstock region 1371-3and reports those measurements to controller 1209. Task 1702 isidentical to task 902 in the first illustrative embodiment, and it willbe clear to those skilled in the art, after reading this disclosure, howto make and use embodiments of the present invention that perform task1701.

At task 1703, thermal sensor 1572-1 periodically measures thetemperature of that portion of workpiece 1206 that is within workpieceregion 1372-1 and reports those measurements to controller 1209.Additionally, thermal sensor 1572-2 periodically measures thetemperature of that portion of workpiece 1206 that is within workpieceregion 1372-2 and reports those measurements to controller 1209. Andfurthermore, thermal sensor 1572-3 periodically measures the temperatureof that portion of workpiece 1206 that is within workpiece region 1372-3and reports those measurements to controller 1209. Task 1703 isidentical to task 903 in the first illustrative embodiment, and it willbe clear to those skilled in the art, after reading this disclosure, howto make and use embodiments of the present invention that perform task1701.

At task 1704, thermal sensor 1373 periodically measures the temperatureof tamping tool 1208 and reports those measurements back to controller1209. Additionally, force gauge 1213 periodically measures the force oftamping tool 1208 on feedstock 1211 at nip line segment 1381 and reportsthose measurements back to controller 1209.

At task 1705:

-   -   (i) optical instrument 1260 irradiates and heats the segment of        feedstock 1211 that is within feedstock region 1371-3, and    -   (ii) optical instrument 1261 irradiates and heats the segment of        feedstock 1211 that is within feedstock region 1371-2,        all as directed by controller 1209. It will be clear to those        skilled in the art, after reading this disclosure, how to make        and use embodiments of the present invention that perform task        1705.

At task 1706:

-   -   (i) optical instrument 1262 irradiates and heats the portion of        workpiece 1206 that is within workpiece region 1372-2, and    -   (ii) optical instrument 1263 irradiates and heats the portion of        workpiece 1206 that is within workpiece region 1372-3,        all as directed by controller 1209. It will be clear to those        skilled in the art, after reading this disclosure, how to make        and use embodiments of the present invention that perform task        1706.

At task 1707:

-   -   (i) optical instrument 1260 adjusts a trait of laser beam 1270        and/or the relationship of laser beam 1270 to the segment of        feedstock 1211 within feedstock region 1371-3, and    -   (ii) optical instrument 1261 adjusts a trait of laser beam 1271        and/or the relationship of laser beam 1271 to the segment of        feedstock 1211 within feedstock region 1371-2, and    -   (iii) optical instrument 1262 adjusts a trait of laser beam 1272        and/or the relationship of laser beam 1272 to the portion of        workpiece 1206 within workpiece region 1372-2, and    -   (iv) optical instrument 1263 adjusts a trait of laser beam 1273        and/or the relationship of laser beam 1273 to the portion of        workpiece 1206 within workpiece region 1372-3,        all as directed by controller 1209. Task 1707 is described in        detail in FIGS. 18, 19, 20, 21, 22, and in the accompanying        text.

At task 1708, additive manufacturing system 1200 deposits a segment offeedstock 1211 onto a portion of workpiece 1206 and tamps the segmentonto the workpiece with tamping tool 1208. It will be clear to thoseskilled in the art, after reading this disclosure, how to make and useembodiments of the present invention that perform task 1708.

FIG. 18 depicts a flowchart of the details of task 1707—adjustingoptical instruments as directed by controller 1209. Optical instrument1260, optical instrument 1261, optical instrument 1262, and opticalinstrument 1263 continually make adjustments, as directed by controller1209, and, therefore, the tasks depicted in FIG. 18 are concurrent.

At task 1801, optical instrument 1260 continually adjusts a trait oflaser beam 1270 and/or the relationship of laser beam 1270 to thesegment of feedstock 1211 within feedstock region 1371-3. Task 1801 isdescribed in detail in FIG. 19 and in the accompanying text.

At task 1802, optical instrument 1261 continually adjusts a trait oflaser beam 1271 and/or the relationship of laser beam 1271 to thesegment of feedstock 1211 within feedstock region 1371-2. Task 1802 isdescribed in detail in FIG. 20 and in the accompanying text.

At task 1803, optical instrument 1262 continually adjusts a trait oflaser beam 1272 and/or the relationship of laser beam 1272 to theportion of workpiece 1206 within workpiece region 1372-2. Task 1803 isdescribed in detail in FIG. 21 and in the accompanying text.

At task 1804, optical instrument 1263 continually adjusts a trait oflaser beam 1273 and/or the relationship of laser beam 1273 to theportion of workpiece 1206 within workpiece region 1372-3. Task 1804 isdescribed in detail in FIG. 22 and in the accompanying text.

FIG. 19 depicts a flowchart of the details of task 1801—adjustingoptical instrument 1260. Controller 1209 continually directs opticalinstrument 1260 to make adjustments, and, therefore, the tasks depictedin FIG. 19 are concurrent.

At task 1901, controller 1209 directs optical instrument 1260 toadjust—lengthen or shorten—the length of feedstock region 1371-3 (i.e.,the length of feedstock 1211 being irradiated by laser beam 1270). Thisprovides controller 1209 with a mechanism for adjusting the temperatureof each unit-length of feedstock 1211 when it is deposited and tamped.For example—and assuming that everything else is constant—increasing thelength of feedstock region 1371-3 spreads the heat energy of laser beam1270 over a greater length of feedstock, which decreases the rate atwhich each unit-length of feedstock is heated. Conversely, decreasingthe length of feedstock region 1371-3 concentrates the heat energy,which increases the rate at which each unit-length of feedstock isheated. It will be clear to those skilled in the art, after reading thisdisclosure, that being able to adjust the length of feedstock region1371-3 is advantageous for, among other things, compensating forvariations in the rate at which feedstock 1211 is deposited and tamped.

At task 1902, controller 1209 directs optical instrument 1260 toadjust—increase or decrease—the distance between pinch line segment 1382and feedstock region 1371-3. This provides controller 1209 with amechanism for adjusting the temperature of each unit-length of feedstock1211 when it is deposited and tamped. For example—and assumingeverything else is constant—increasing the distance gives eachunit-length of feedstock more time to cool before it is deposited andtamped. Conversely, decreasing the distance gives each unit segment offeedstock less time to cool before it is deposited and tamped. It willbe clear to those skilled in the art, after reading this disclosure,that being able to adjust the distance between pinch line segment 1382and feedstock region 1371-3 is advantageous for, among other things,fine tuning the temperature of each unit-length of feedstock 1211 at thetime that it is deposited and tamped.

At task 1903, controller 1209 directs optical instrument 1260 to adjustthe irradiance of laser beam 1270 on each unit-length of feedstock 1211within feedstock region 1371-3. This provides controller 1209 with amechanism for adjusting the temperature of each unit-length of feedstock1211 when it is deposited and tamped. For example—and assumingeverything else is constant—increasing the irradiance on a unit-lengthof feedstock 1211 increases the rate at which it is heated. Conversely,decreasing the irradiance on a unit-length of feedstock 1211 decreasesthe rate at which it is heated. It will be clear to those skilled in theart, after reading this disclosure, that being able to adjust theirradiance of laser beam 1270 on feedstock 1211 is advantageous for,among other things, compensating for variations in the angle ofincidence of laser beam 1270 on feedstock 1211 caused by changes in therelative position of optical instrument 1260 to feedstock 1211. Thesechanges are often caused by changes in the contour of workpiece 1206.

At task 1904, controller 1209 directs optical instrument 1260 to adjustthe angle of incidence of laser beam 1270 on feedstock 1211 withinfeedstock region 1371-3. This provides controller 1209 with anothermechanism for adjusting the temperature of each unit-length of feedstock1211 when it is deposited and tamped. For example—and assumingeverything else is constant—adjusting the angle of incidence of laserbeam 1270 on feedstock 1211 changes the effective irradiance on eachunit-length of feedstock 1211. It will be clear to those skilled in theart, after reading this disclosure, that being able to adjust the angleof incidence of laser beam 1270 on feedstock 1211 is advantageous for,among other things, compensating for changes in the relative position ofoptical instrument 1260 to feedstock 1211. These changes are oftencaused by changes in the contour of workpiece 1206.

FIG. 20 depicts a flowchart of the details of task 1802—adjustingoptical instrument 1261. Controller 1209 continually directs opticalinstrument 1261 to make adjustments, and, therefore, the tasks depictedin FIG. 20 are concurrent.

At task 2001, controller 1209 directs optical instrument 1261 toadjust—lengthen or shorten—the length of feedstock region 1371-2 (i.e.,the length of feedstock 1211 being irradiated by laser beam 1271). Thisprovides controller 1209 with a mechanism for adjusting the temperatureof each unit-length of feedstock 1211 when it is deposited and tamped.For example—and assuming that everything else is constant—increasing thelength of feedstock region 1371-2 spreads the heat energy of laser beam1271 over a greater length of feedstock, which decreases the rate atwhich each unit-length of feedstock is heated. Conversely, decreasingthe length of feedstock region 1371-2 concentrates the heat energy,which increases the rate at which each unit-length of feedstock isheated. It will be clear to those skilled in the art, after reading thisdisclosure, that being able to adjust the length of feedstock region1371-2 is advantageous for, among other things, compensating forvariations in the rate at which feedstock 1211 is deposited and tamped.

At task 2002, controller 1209 directs optical instrument 1261 toadjust—increase or decrease—the distance between pinch line segment 1382and feedstock region 1371-2. This provides controller 1209 with amechanism for adjusting the temperature of each unit-length of feedstock1211 when it is deposited and tamped. For example—and assumingeverything else is constant—increasing the distance gives eachunit-length of feedstock more time to cool before it is deposited andtamped. Conversely, decreasing the distance gives each unit segment offeedstock less time to cool before it is deposited and tamped. It willbe clear to those skilled in the art, after reading this disclosure,that being able to adjust the distance between pinch line segment 1382and feedstock region 1371-2 is advantageous for, among other things,fine tuning the temperature of each unit-length of feedstock 1211 at thetime that it is deposited and tamped.

At task 2003, controller 1209 directs optical instrument 1261 to adjustthe irradiance of laser beam 1271 on each unit-length of feedstock 1211within feedstock region 1371-2. This provides controller 1209 with amechanism for adjusting the temperature of each unit-length of feedstock1211 when it is deposited and tamped. For example—and assumingeverything else is constant—increasing the irradiance on a unit-lengthof feedstock 1211 increases the rate at which it is heated. Conversely,decreasing the irradiance on a unit-length of feedstock 1211 decreasesthe rate at which it is heated. It will be clear to those skilled in theart, after reading this disclosure, that being able to adjust theirradiance of laser beam 1271 on feedstock 1211 is advantageous for,among other things, compensating for variations in the angle ofincidence of laser beam 1271 on feedstock 1211 caused by changes in therelative position of optical instrument 1261 to feedstock 1211. Thesechanges are often caused by changes in the contour of workpiece 1206.

At task 2004, controller 1209 directs optical instrument 1261 to adjustthe angle of incidence of laser beam 1271 on feedstock 1211 withinfeedstock region 1371-2. This provides controller 1209 with anothermechanism for adjusting the temperature of each unit-length of feedstock1211 when it is deposited and tamped. For example—and assumingeverything else is constant—adjusting the angle of incidence of laserbeam 1271 on feedstock 1211 changes the effective irradiance on eachunit-length of feedstock 1211. It will be clear to those skilled in theart, after reading this disclosure, that being able to adjust the angleof incidence of laser beam 1271 on feedstock 1211 is advantageous for,among other things, compensating for changes in the relative position ofoptical instrument 1261 to feedstock 1211. These changes are oftencaused by changes in the contour of workpiece 1206.

FIG. 21 depicts a flowchart of the details of task 1803—adjustingoptical instrument 1262. Controller 1209 continually directs opticalinstrument 1262 to make adjustments, and, therefore, the tasks depictedin FIG. 21 are concurrent.

At task 2101, controller 1209 directs optical instrument 1262 toadjust—lengthen or shorten—the length of workpiece region 1372-2 (i.e.,the portion of workpiece 1206 being irradiated by laser beam 1272). Thisprovides controller 1209 with a mechanism for adjusting the temperatureof each unit portion of workpiece 1206 when it is deposited and tamped.For example—and assuming that everything else is constant—increasing thelength of workpiece region 1372-2 spreads the heat energy of laser beam1272 over a greater portion of workpiece 1206, which decreases the rateat which each unit portion of workpiece 1206 is heated. Conversely,decreasing the length of workpiece region 1372-2 concentrates the heatenergy, which increases the rate at which each unit portion of workpiece1206 is heated. It will be clear to those skilled in the art, afterreading this disclosure, that being able to adjust the length ofworkpiece region 1372-2 is advantageous for, among other things,compensating for variations in the rate at which feedstock 1211 isdeposited and tamped.

At task 2102, controller 1209 directs optical instrument 1262 toadjust—increase or decrease—the distance between pinch line 1382 andworkpiece region 1372-2. This provides controller 1209 with a mechanismfor adjusting the temperature of each unit portion of workpiece 1206when it is deposited and tamped. For example—and assuming everythingelse is constant—increasing the distance gives each unit portion ofworkpiece 1206 more time to cool before it is deposited and tamped.Conversely, decreasing the distance gives each unit segment of feedstockless time to cool before it is deposited and tamped. It will be clear tothose skilled in the art, after reading this disclosure, that being ableto adjust the distance between pinch line segment 1382 and workpieceregion 1372-2 is advantageous for, among other things, fine tuning thetemperature of each unit portion of workpiece 1206 at the time that thecorresponding segment of feedstock 1211 is deposited and tamped.

At task 2103, controller 1209 directs optical instrument 1262 to adjustthe irradiance of laser beam 1272 on each unit portion of workpiece 1206within workpiece region 1372-2. This provides controller 1209 with amechanism for adjusting the temperature of each unit portion ofworkpiece 1206 at the time that the corresponding segment of feedstock1211 is deposited and tamped. For example—and assuming everything elseis constant—increasing the irradiance on a unit portion of workpiece1206 increases the rate at which it is heated. Conversely, decreasingthe irradiance on a unit-area of workpiece 1206 decreases the rate atwhich it is heated. It will be clear to those skilled in the art, afterreading this disclosure, that being able to adjust the irradiance oflaser beam 1272 on workpiece 1206 is advantageous for, among otherthings, compensating for variations in the angle of incidence of laserbeam 1272 on workpiece 1206 caused by changes in the relative positionof optical instrument 1262 to workpiece 1206. These changes are oftencaused by changes in the contour of workpiece 1206.

At task 2104, controller 1209 directs optical instrument 1262 to adjustthe angle of incidence of laser beam 1272 on workpiece 1206 withinworkpiece region 1372-2. This provides controller 1209 with anothermechanism for adjusting the temperature of each unit portion ofworkpiece 1206 when it is deposited and tamped. For example—and assumingeverything else is constant—adjusting the angle of incidence of laserbeam 1272 on workpiece 1206 changes the effective irradiance on eachunit portion of workpiece 1206. It will be clear to those skilled in theart, after reading this disclosure, that being able to adjust the angleof incidence of laser beam 1272 on workpiece 1206 is advantageous for,among other things, compensating for changes in the relative position ofoptical instrument 1262 to workpiece 1206. These changes are oftencaused by changes in the contour of workpiece 1206.

At task 2105, controller 1209 directs optical instrument 1262 to steerlaser beam 1272 onto deposition path 1391.

In accordance with the second illustrative, sensor array 1215 is notmechanically steered onto workpiece region 1372-1, workpiece region1372-2, or workpiece region 1372-3. Instead, controller 1209 picks thetemperature measurements for workpiece region 1372-1, workpiece region1372-2, or workpiece region 1372-3 out of the thermal image from sensorarray 1215 based on the location of deposition path 1391 in that image.It will be clear to those skilled in the art, after reading thisdisclosure, how to accomplish this.

FIG. 22 depicts a flowchart of the details of task 1804—adjustingoptical instrument 1263. Controller 1209 continually directs opticalinstrument 1263 to make adjustments, and, therefore, the tasks depictedin FIG. 22 are concurrent.

At task 2201, controller 1209 directs optical instrument 1263 toadjust—lengthen or shorten—the length of workpiece region 1372-3 (i.e.,the portion of workpiece 1206 being irradiated by laser beam 1273). Thisprovides controller 1209 with a mechanism for adjusting the temperatureof each unit portion of workpiece 1206 when it is deposited and tamped.For example—and assuming that everything else is constant—increasing thelength of workpiece region 1372-3 spreads the heat energy of laser beam1273 over a greater portion of workpiece 1206, which decreases the rateat which each unit portion of workpiece 1206 is heated. Conversely,decreasing the length of workpiece region 1372-3 concentrates the heatenergy, which increases the rate at which each unit portion of workpiece1206 is heated. It will be clear to those skilled in the art, afterreading this disclosure, that being able to adjust the length ofworkpiece region 1372-3 is advantageous for, among other things,compensating for variations in the rate at which feedstock 1211 isdeposited and tamped.

At task 2202, controller 1209 directs optical instrument 1263 toadjust—increase or decrease—the distance between pinch line 1382 andworkpiece region 1372-3. This provides controller 1209 with a mechanismfor adjusting the temperature of each unit portion of workpiece 1206when it is deposited and tamped. For example—and assuming everythingelse is constant—increasing the distance gives each unit portion ofworkpiece 1206 more time to cool before it is deposited and tamped.Conversely, decreasing the distance gives each unit segment of feedstockless time to cool before it is deposited and tamped. It will be clear tothose skilled in the art, after reading this disclosure, that being ableto adjust the distance between pinch line segment 1382 and workpieceregion 1372-3 is advantageous for, among other things, fine tuning thetemperature of each unit portion of workpiece 1206 at the time that thecorresponding segment of feedstock 1211 is deposited and tamped.

At task 2203, controller 1209 directs optical instrument 1263 to adjustthe irradiance of laser beam 1273 on each unit portion of workpiece 1206within workpiece region 1372-3. This provides controller 1209 with amechanism for adjusting the temperature of each unit portion ofworkpiece 1206 at the time that the corresponding segment of feedstock1211 is deposited and tamped. For example—and assuming everything elseis constant—increasing the irradiance on a unit portion of workpiece1206 increases the rate at which it is heated. Conversely, decreasingthe irradiance on a unit-area of workpiece 1206 decreases the rate atwhich it is heated. It will be clear to those skilled in the art, afterreading this disclosure, that being able to adjust the irradiance oflaser beam 1273 on workpiece 1206 is advantageous for, among otherthings, compensating for variations in the angle of incidence of laserbeam 1273 on workpiece 1206 caused by changes in the relative positionof optical instrument 1263 to workpiece 1206. These changes are oftencaused by changes in the contour of workpiece 1206.

At task 2204, controller 1209 directs optical instrument 1263 to adjustthe angle of incidence of laser beam 1273 on workpiece 1206 withinworkpiece region 1372-3. This provides controller 1209 with anothermechanism for adjusting the temperature of each unit portion ofworkpiece 1206 when it is deposited and tamped. For example—and assumingeverything else is constant—adjusting the angle of incidence of laserbeam 1273 on workpiece 1206 changes the effective irradiance on eachunit portion of workpiece 1206. It will be clear to those skilled in theart, after reading this disclosure, that being able to adjust the angleof incidence of laser beam 1273 on workpiece 1206 is advantageous for,among other things, compensating for changes in the relative position ofoptical instrument 1263 to workpiece 1206. These changes are oftencaused by changes in the contour of workpiece 1206.

At task 2205, controller 1209 directs optical instrument 1263 to steerlaser beam 1273 onto deposition path 1391.

FIG. 23 depicts a flowchart of the relative timing of the tasksperformed on segment m of feedstock 1211 and on portion n of workpiece1206, wherein m and n are integers. In accordance with the secondillustrative embodiment segment m of feedstock 1211 is deposited andtamped onto portion n of workpiece 1206.

During time-interval Δt=m−3, the temperature of segment m of feedstock1211 is measured by thermal sensor 1571-1 and reported to controller1209.

During time-interval Δt=n−3, the temperature of portion n of workpiece1206 is measured by thermal sensor 1572-1 and reported to controller1209.

In accordance with the second illustrative embodiment, the duration oftime-interval Δt=m−3 equals the duration of time-interval Δt=n−3, andtime-interval Δt=m−3 is contemporaneous with time-interval Δt=n−3. Itwill be clear to those skilled in the art, however, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which the duration of time-interval Δt=m−3 does not equalthe duration of time-interval Δt=n−3. Furthermore, it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments of the present invention in whichtime-interval Δt=m−3 is not contemporaneous with time-interval Δt=n−3.And still furthermore, it will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=m−3overlaps, immediately precedes, immediately succeeds, precedes but notimmediately, or succeeds but not immediately time-interval Δt=n−3.

During time-interval Δt=m−2:

-   -   (i) controller 1209 directs feedstock laser 1241 to generate        laser beam 1271 with a given average power, and    -   (ii) controller 1209 directs optical instrument 1261 to adjust a        trait of laser beam 1271 and/or the relationship of laser beam        1271 to feedstock 1211, and    -   (iii) optical instrument 1261 irradiates and heats segment m of        feedstock 1211, and    -   (iv) the temperature of segment m of feedstock 1211 is measured        by thermal sensor 1571-2 and reported to controller 1209.        In accordance with the second illustrative embodiment, the        duration of time-interval Δt=m−2 equals the duration of Δt=m−3.        It will be clear to those skilled in the art, however, after        reading this disclosure, how to make and use alternative        embodiments of the present invention in which the duration of        time-interval Δt=m−2 does not equal the duration of time        interval Δt=m−3. Furthermore, in accordance with the second        illustrative embodiment, time-interval Δt=m−2 is after, and is        mutually-exclusive of, time-interval Δt=m−3. It will be clear to        those skilled in the art, however, after reading this        disclosure, how to make and use alternative embodiments of the        present invention in which time-interval Δt=m−2 overlaps,        immediately succeeds, or succeeds but not immediately,        time-interval Δt=m−3.

During time-interval Δt=n−2:

-   -   (i) controller 1209 directs workpiece laser 1242 to generate        laser beam 1272 with a given average power, and    -   (ii) controller 1209 directs optical instrument 1262 to adjust a        trait of laser beam 1272 and/or the relationship of laser beam        1272 to workpiece 1206, and    -   (iii) controller 1209 directs optical instrument 1262 to steer        laser beam 1272 onto deposition path 1391, and    -   (iv) optical instrument 1262 irradiates and heats portion n of        workpiece 1206, and    -   (v) the temperature of portion n of workpiece 1206 is measured        by thermal sensor 1572-2 and reported to controller 1209.

In accordance with the second illustrative embodiment, the duration oftime-interval Δt=n−2 equals the duration of Δt=n−3. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichthe duration of time-interval Δt=n−2 does not equal the duration of timeinterval Δt=n−3. Furthermore, in accordance with the second illustrativeembodiment, time-interval Δt=n−2 is after, and is mutually-exclusive of,time-interval Δt=n−3. It will be clear to those skilled in the art,however, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=n−2overlaps, immediately succeeds, or succeeds but not immediately,time-interval Δt=n−3.

In accordance with the second illustrative embodiment, the duration oftime-interval Δt=m−2 equals the duration of time-interval Δt=n−2, andtime-interval Δt=m−2 is contemporaneous with time-interval Δt=n−2. Itwill be clear to those skilled in the art, however, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which the duration of time-interval Δt=m−2 does not equalthe duration of time-interval Δt=n−2. Furthermore, it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments of the present invention in whichtime-interval Δt=m−2 is not contemporaneous with time-interval Δt=n−2.And still furthermore, it will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=m−2overlaps, immediately precedes, immediately succeeds, precedes but notimmediately, or succeeds but not immediately time-interval Δt=n−2.

During time-interval Δt=m−1:

-   -   (i) controller 1209 directs feedstock laser 1240 to generate        laser beam 1270 with a given average power, and    -   (ii) controller 1209 directs optical instrument 1260 to adjust a        trait of laser beam 1270 and/or the relationship of laser beam        1270 to feedstock 1211, and    -   (iii) optical instrument 1260 irradiates and heats segment m of        feedstock 1211, and    -   (iv) the temperature of segment m of feedstock 1211 is measured        by thermal sensor 1571-3 and reported to controller 1209.

In accordance with the second illustrative embodiment, the duration oftime-interval Δt=m−1 equals the duration of Δt=m−2. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichthe duration of time-interval Δt=m−1 does not equal the duration of timeinterval Δt=m−2. Furthermore, in accordance with the second illustrativeembodiment, time-interval Δt=m−1 is after, and is mutually-exclusive of,time-interval Δt=m−2. It will be clear to those skilled in the art,however, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=m−1overlaps, immediately succeeds, or succeeds but not immediately,time-interval Δt=m−2.

During time-interval Δt=n−1:

-   -   (i) controller 1209 directs workpiece laser 1243 to generate        laser beam 1273 with a given average power, and    -   (ii) controller 1209 directs optical instrument 1263 to adjust a        trait of laser beam 1273 and/or the relationship of laser beam        1273 to workpiece 1206, and    -   (iii) controller 1209 directs optical instrument 1263 to steer        laser beam 1273 onto deposition path 1391, and    -   (iv) optical instrument 1263 irradiates and heats portion n of        workpiece 1206, and    -   (v) the temperature of portion n of workpiece 1206 is measured        by thermal sensor 1572-3 and reported to controller 1209.

In accordance with the second illustrative embodiment, the duration oftime-interval Δt=n−1 equals the duration of Δt=n−2. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichthe duration of time-interval Δt=n−1 does not equal the duration of timeinterval Δt=n−2. Furthermore, in accordance with the second illustrativeembodiment, time-interval Δt=n−1 is after, and is mutually-exclusive of,time-interval Δt=n−2. It will be clear to those skilled in the art,however, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=n−1overlaps, immediately succeeds, or succeeds but not immediately,time-interval Δt=n−2.

In accordance with the second illustrative embodiment, the duration oftime-interval Δt=m−1 equals the duration of time-interval Δt=n−1, andtime-interval Δt=m−1 is contemporaneous with time-interval Δt=n−1. Itwill be clear to those skilled in the art, however, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which the duration of time-interval Δt=m−1 does not equalthe duration of time-interval Δt=n−1. Furthermore, it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments of the present invention in whichtime-interval Δt=m−1 is not contemporaneous with time-interval Δt=n−1.And still furthermore, it will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=m−1overlaps, immediately precedes, immediately succeeds, precedes but notimmediately, or succeeds but not immediately time-interval Δt=n−1.

During time-interval Δt=m=n, segment m of feedstock 1211 is depositedand tamped onto portion n of workpiece 1206.

In accordance with the second illustrative embodiment, the duration oftime-interval Δt=m equals the duration of Δt=m−1. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichthe duration of time-interval Δt=m does not equal the duration of timeinterval Δt=m−1. Furthermore, in accordance with the second illustrativeembodiment, time-interval Δt=m is after, and is mutually-exclusive of,time-interval Δt=m−1. It will be clear to those skilled in the art,however, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=moverlaps, immediately succeeds, or succeeds but not immediately,time-interval Δt=m−1.

In accordance with the second illustrative embodiment, the duration oftime-interval Δt=n equals the duration of Δt=n−1. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichthe duration of time-interval Δt=n does not equal the duration of timeinterval Δt=n−1. Furthermore, in accordance with the second illustrativeembodiment, time-interval Δt=n is after, and is mutually-exclusive of,time-interval Δt=n−1. It will be clear to those skilled in the art,however, after reading this disclosure, how to make and use alternativeembodiments of the present invention in which time-interval Δt=noverlaps, immediately succeeds, or succeeds but not immediately,time-interval Δt=n−1.

FIG. 24 depicts an illustration of additive manufacturing system 2400 inaccordance with the third illustrative embodiment of the presentinvention. Additive manufacturing system 2400 fabricates an article ofmanufacture by successively depositing segments of fiber-reinforcedthermoplastic feedstock (e.g., filament, tape, etc.) onto a workpieceuntil the article of manufacture is complete.

Additive manufacturing system 2400 is identical to additivemanufacturing system 1200 fabricates in that they both fabricate anarticle of manufacture by successively depositing segments offiber-reinforced thermoplastic feedstock (e.g., filament, tape, etc.)onto a workpiece until the article of manufacture is complete.Furthermore, most of the components of system 2400 are identical totheir counterparts in system 1200 and perform exactly the same functionin exactly the same way.

For example, the heating and sensor architecture for additivemanufacturing system 2400 is identical to that for additivemanufacturing system 1200 as described in FIG. 15 and the accompanyingtext. The sensor and control architecture for that portion of additivemanufacturing system 2400 is identical to that for additivemanufacturing system 1200 as described in FIG. 16 and the accompanyingtext. A flowchart of the tasks performed by additive manufacturingsystem 2400 is identical to that for additive manufacturing system 1200as described in FIGS. 17, 18, 19, 20, and 21. And a flowchart of therelative timing of the tasks performed by additive manufacturing system2400 is identical to that for additive manufacturing system 1200 asdescribed in FIG. 22.

In contrast, additive manufacturing system 2400 is unlike additivemanufacturing system 1200 in that system 2400:

-   -   (i) multiplexes the laser beams onto a single optical cable for        transport between the lasers and deposition head 1207, and    -   (ii) employs lasers whose laser beams are characterized by        different wavelengths to facilitate the multiplexing and        demultiplexing of the laser beams.        U.S. patent application Ser. No. 16/690,765, entitled “Heater        for Thermoplastic Filament and Workpiece,” filed Nov. 21, 2019        is incorporated by reference for the purpose of disclosing:    -   (i) multi-beam heating systems for additive manufacturing of        fiber-reinforced thermoplastics, and    -   (ii) one- and two-stage laser heating systems for        fiber-reinforced thermoplastic feedstock (e.g., filament, tape,        etc), and    -   (iii) one- and two-stage laser heating system for        fiber-reinforced thermoplastic workpieces, and    -   (iv) multiplexing laser beams for use in the heating of        fiber-reinforced feedstock and workpieces.

Additive manufacturing system 2400 comprises: platform 1201, robot mount1202, robot 1203, build plate support 1204, build plate 1205, workpiece1206, deposition head 2407, tamping tool 1208, controller 1209,feedstock reel 1210, feedstock 1211, accumulator 1212, force gauge 1213,sensor array 1215, feedstock laser 2440, feedstock laser 2441, workpiecelaser 2442, feedstock laser 2443, optical cable 2454, sensor cable 1254,optical instrument 1260, optical instrument 1261, optical instrument1262, optical instrument 1263, laser beam 1270, laser beam 1271, laserbeam 1272, laser beam 1273, feedstock laser control cable 1291,workpiece laser control cable 1292, beam combiner 2451, beam combiner2452, beam combiner 2453, beam splitter 2461, beam splitter 2462, andbeam splitter 2463, interrelated as shown.

FIG. 25 depicts a close-up of workpiece 1206, deposition head 2407,tamping tool 1208, feedstock 1211, sensor array 1215, optical instrument1260, optical instrument 1261, optical instrument, 1262, opticalinstrument 1263, optical cable 2454, sensor cable 1254, laser beam 1270,laser beam 1271, laser beam 1272, laser beam 1273, feedstock region1371-1, feedstock region 1371-2, feedstock region 1371-3, workpieceregion 1372-1, workpiece region 1372-2, workpiece region 1372-3, nipline segment 1381, and pinch line segment 1382, beam splitter 2461, beamsplitter 2462, and beam splitter 2463, interrelated as shown.

Deposition head 2407 is identical to deposition head 1207 except that isalso comprises beam splitter 2461, beam splitter 2462, and beam splitter2463, and structural support for beam splitter 2461, beam splitter 2462,and beam splitter 2463.

Feedstock laser 2440 is identical to feedstock laser 1240 in that itgenerates laser beam 1270 for optical instrument 1260. It will be clearto those skilled in the art how to make and use feedstock laser 2440.

Feedstock laser 2441 is identical to feedstock laser 1241 in that itgenerates laser beam 1271 for optical instrument 1261 except that it ischaracterized by a wavelength λ=905 nm. It will be clear to thoseskilled in the art how to make and use feedstock laser 2441.

Workpiece laser 2442 is identical to workpiece laser 1242 in that itgenerates laser beam 1272 for optical instrument 1262 except that it ischaracterized by a wavelength λ=955 nm. It will be clear to thoseskilled in the art how to make and use workpiece laser 2441.

Workpiece laser 2443 is identical to workpiece laser 1243 in that itgenerates laser beam 1273 for optical instrument 1263 except that it ischaracterized by a wavelength λ=930 nm. It will be clear to thoseskilled in the art how to make and use workpiece laser 2442.

Optical cable 2454 is a glass fiber, in well-known fashion, that carrieslaser beam 1270, laser beam 1271, laser beam 1272, and laser beam 1273from feedstock laser 2441 from beam combiner 2453 to beam splitter 2462with substantially no loss. It will be clear to those skilled in the arthow to make and use optical cable 2454.

Beam combiner 2451 is a dichroic beam combiner, in well-known fashion,that combines laser beam 1270 and laser beam 1271. It will be clear tothose skilled in the art how to make and use beam combiner 2451.

Beam combiner 2452 is a dichroic beam combiner, in well-known fashion,that combines laser beam 1272 to the combination of laser beam 1270 andlaser beam 1271. It will be clear to those skilled in the art how tomake and use beam combiner 2452.

Beam combiner 2453 is a dichroic beam combiner, in well-known fashion,that combines laser beam 1273 to the combination of laser beam 1270,laser beam 1271, and laser beam 1272. It will be clear to those skilledin the art how to make and use beam combiner 2453.

Beam splitter 2462 is a dichroic beam splitter, in well-known fashion,that splits laser beam 1272 from the combination of laser beam 1270,laser beam 1271, laser beam 1272, and laser beam 1273. It will be clearto those skilled in the art how to make and use beam splitter 2462.

Beam splitter 2463 is a dichroic beam splitter, in well-known fashion,that splits laser beam 1273 from the combination of laser beam 1270,laser beam 1271, and laser beam 1273. It will be clear to those skilledin the art how to make and use beam splitter 2463.

Beam splitter 2461 is a dichroic beam splitter, in well-known fashion,that splits laser beam 1270 and laser beam 1271 from the combination oflaser beam 1270 and laser beam 1271. It will be clear to those skilledin the art how to make and use beam splitter 2461.

The sensor and control architecture for that portion of additivemanufacturing system 2400 is identical to that for additivemanufacturing system 1200 as described in FIG. 16 and the accompanyingtext.

A flowchart of the tasks performed by additive manufacturing system 2400is identical to that for additive manufacturing system 1200 as describedin FIGS. 17, 18, 19, 20, and

A flowchart of the relative timing of the tasks performed by additivemanufacturing system 2400 is identical to that for additivemanufacturing system 1200 as described in FIG. 22.

FIG. 26 depicts a schematic diagram of the heating and sensorarchitecture for additive manufacturing system 2400, which irradiatesand heats feedstock 1211 and workpiece 1206 and measures the temperatureof feedstock 1211, workpiece 1206, and tamping tool 1208. In mostrespects, the heating and sensor architecture for additive manufacturingsystem 2400 is identical to that for system 1200, except for theaddition of the multiplexing of laser beams. To wit, and as shown inFIG. 26:

-   -   (i) feedstock laser 1240 provides laser beam 1270 to optical        instrument 1260 via beam combiner 2451, optical cable 2454, and        beam splitter 2461, and    -   (ii) feedstock laser 1241 provides laser beam 1271 to optical        instrument 1261 via beam combiner 2451, optical cable 2454, and        beam splitter 2461, and    -   (iii) workpiece laser 1242 provides laser beam 1272 to optical        instrument 1262 via beam combiner 2452, optical cable 2454, and        beam splitter 2462, and    -   (iv) workpiece laser 1243 provides laser beam 1273 to optical        instrument 1263 via beam combiner 2452, optical cable 2454, and        beam splitter 2463.        In all other respects, the heating and sensor system 2400 is        identical to that for system 1200.

Although the third illustrative embodiment employs 4:1 multiplexing, itwill be clear to those skilled in the art, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention that employ N:1 multiplexing, where N is a positive integergreater than 1 (e.g., 2, 3, 5, 6, 7, 8, 10, 20, 500, 100, 500, etc.).

What is claimed is:
 1. A method for additive manufacturing, the methodcomprising: irradiating and heating, with a first laser beam generatedby a first laser, a segment of a feedstock with a first average powerduring a first time-interval; irradiating and heating, with a secondlaser beam generated by a second laser, the segment of the feedstockwith a second average power during a second time-interval, wherein thesecond time-interval is after, and is mutually exclusive of, the firsttime-interval; and tamping, with a tamping tool, the segment of thefeedstock onto a portion of a workpiece during a third time-interval,wherein the third time-interval is after, and is mutually exclusive of,the first time-interval, and wherein the third time-interval is after,and is mutually exclusive of, the second time-interval; depositing thefeedstock onto the workpiece at a non-uniform rate; and directing thefirst laser to generate the first laser beam with the first averagepower during the first time-interval based on: (i) a thermal model ofthe feedstock, and (ii) a prediction of the interval between the firsttime-interval and the third time-interval.
 2. The method of claim 1further comprising: measuring a temperature of the segment of thefeedstock in a fourth time-interval; and directing the first laser togenerate the first laser beam with the first average power during thefirst time-interval based on the temperature.
 3. The method of claim 1further comprising: measuring a temperature of the segment of thefeedstock in the first time-interval; and directing the first laser togenerate the first laser beam with the first average power during thefirst time-interval based on the temperature.
 4. The method of claim 1:wherein the first laser beam is characterized by a first wavelength;wherein the second laser beam is characterized by a second wavelength;and wherein the first wavelength does not equal the second wavelength.5. The method of claim 1: wherein the first laser beam is characterizedby a first wavelength; wherein the second laser beam is characterized bya second wavelength; and wherein the first wavelength equals the secondwavelength.
 6. The method of claim 1: wherein the first laser beam ischaracterized by a first wavelength; wherein the second laser beam ischaracterized by a second wavelength; and wherein the first wavelengthdoes not equal the second wavelength; and further comprising: a firstoptical beam splitter for receiving a spatial combination of the firstlaser beam and the second laser beam and for spatially separating thefirst laser beam and the second laser beam.
 7. The method of claim 1wherein the tamping tool is a roller.
 8. The method of claim 1 whereinthe tamping tool is a roller whose tangential speed equals a linearspeed of the feedstock adjacent to the roller.
 9. The method of claim 1further comprising: irradiating and heating, with a third laser beamgenerated by a third laser, the portion of the workpiece with a thirdaverage power during a fourth time interval, wherein the thirdtime-interval is after, and is mutually exclusive of, the fourthtime-interval.
 10. A method for additive manufacturing, the methodcomprising: irradiating and heating, with a first laser beam generatedby a first laser, a portion of a workpiece with a first average powerduring a first time-interval; irradiating and heating, with a secondlaser beam generated by a second laser, the portion of the workpiecewith a second average power during a second time-interval, wherein thesecond time-interval is after, and is mutually exclusive of, the firsttime-interval; and tamping, with a tamping tool, a segment of afeedstock onto the portion of the workpiece during a thirdtime-interval, wherein the third time-interval is after, and is mutuallyexclusive of, the first time-interval, and wherein the thirdtime-interval is after, and is mutually exclusive of, the secondtime-interval; depositing the feedstock onto the workpiece at anon-uniform rate; and directing the first laser to generate the firstlaser beam with the first average power during the first time-intervalbased on: (i) a thermal model of the workpiece, and (ii) a prediction ofthe interval between the first time-interval and the thirdtime-interval.
 11. The method of claim 10 further comprising: measuringa temperature of the portion of the workpiece in a fourth time-interval;and directing the first laser to generate the first laser beam with thefirst average power during the first time-interval based on thetemperature.
 12. The method of claim 10 further comprising: measuring atemperature of the portion of the workpiece in the first time-interval;and directing the first laser to generate the first laser beam with thefirst average power during the first time-interval based on thetemperature.
 13. The method of claim 10: wherein the first laser beam ischaracterized by a first wavelength; wherein the second laser beam ischaracterized by a second wavelength; and wherein the first wavelengthdoes not equal the second wavelength.
 14. The method of claim 10:wherein the first laser beam is characterized by a first wavelength;wherein the second laser beam is characterized by a second wavelength;and wherein the first wavelength equals the second wavelength.
 15. Themethod of claim 10: wherein the first laser beam is characterized by afirst wavelength; wherein the second laser beam is characterized by asecond wavelength; and wherein the first wavelength does not equal thesecond wavelength; and further comprising: a first optical beam splitterfor receiving a spatial combination of the first laser beam and thesecond laser beam and for spatially separating the first laser beam andthe second laser beam.
 16. The method of claim 10 wherein the tampingtool is a roller.
 17. The method of claim 10 wherein the tamping tool isa roller whose tangential speed equals a linear speed of the feedstockadjacent to the roller.
 18. The method of claim 10 further comprising:irradiating and heating, with a third laser beam generated by a thirdlaser, the segment of the feedstock with a third average power during afourth time interval, wherein the third time-interval is after, and ismutually exclusive of, the fourth time-interval.